Slimefun4 - API 
Package Description
io.github.thebusybiscuit.slimefun4.api
This package contains a bunch of classes and sub-packages related to the interaction with Slimefun via an API.
io.github.thebusybiscuit.slimefun4.api.events
This package contains all extensions of Event that Slimefun provides and allows you to listen to.
io.github.thebusybiscuit.slimefun4.api.exceptions
This package contains all different extensions of Exception that Slimefun uses internally.
io.github.thebusybiscuit.slimefun4.api.geo
This package contains classes that are centered around the GEOResource API.
io.github.thebusybiscuit.slimefun4.api.gps
This package stores classes of the API that are related to the GPSNetwork.
io.github.thebusybiscuit.slimefun4.api.items
This package contains a few classes that revolve around the API for SlimefunItem, such as ItemSetting
io.github.thebusybiscuit.slimefun4.api.network
This package provides the API infrastructure for networks, such as the Cargo- or Energy net.
io.github.thebusybiscuit.slimefun4.api.player
This package stores API-related classes that are related to a Player, such as the PlayerProfile for example.
Slimefun4 - Core packages 
Package Description
io.github.thebusybiscuit.slimefun4.core
This package holds the core systems of Slimefun, these are not neccessarily used as an API but ratherprovide the core functionality of this Plugin.
io.github.thebusybiscuit.slimefun4.core.attributes
This package contains all variations of ItemAttribute that can be assigned to a SlimefunItem
io.github.thebusybiscuit.slimefun4.core.categories
This package stores API classes that are centered around the extension of the Category class, such as SeasonalCategory for example.
io.github.thebusybiscuit.slimefun4.core.commands
This package contains everything related to slimefun's ingame command.
io.github.thebusybiscuit.slimefun4.core.commands.subcommands
This package holds all implementations of SubCommand.
io.github.thebusybiscuit.slimefun4.core.guide
This package contains the core system for the SlimefunGuide.
io.github.thebusybiscuit.slimefun4.core.guide.options
This package contains the Settings menu forthe SlimefunGuide as well as the interface SlimefunGuideOption for adding your own options
io.github.thebusybiscuit.slimefun4.core.networks.cargo
This package holds an implementation of Network that is responsible for item transportation.
io.github.thebusybiscuit.slimefun4.core.networks.energy
This package holds an implementation of Network that is responsible for transmitting energy.
io.github.thebusybiscuit.slimefun4.core.services
This package provides a few "Services" that Slimefun uses.
io.github.thebusybiscuit.slimefun4.core.services.github
This package contains everything related to GitHub and contributors.
io.github.thebusybiscuit.slimefun4.core.services.localization
This package contains everything related to translations and localization.
io.github.thebusybiscuit.slimefun4.core.services.metrics
This package contains everything related to bStats Metrics
io.github.thebusybiscuit.slimefun4.core.services.plugins
This package contains all hooks to external plugins
Slimefun4 - Implementations 
Package Description
io.github.thebusybiscuit.slimefun4.implementation.guide
This package provides the different implementations of our SlimefunGuide
io.github.thebusybiscuit.slimefun4.implementation.listeners
This package contains all implementations of Listener that Slimefun uses.
io.github.thebusybiscuit.slimefun4.implementation.resources
This package contains all implementations of GEOResource.
io.github.thebusybiscuit.slimefun4.implementation.setup
In this package we initialize our items, researches and stuff.
io.github.thebusybiscuit.slimefun4.implementation.tasks
This package contains several tasks that Slimefun runs regularly.
Slimefun4 - Common utility packages 
Package Description
io.github.thebusybiscuit.slimefun4.utils
This package contains some utility classes that offer handy ways to do stuff.
io.github.thebusybiscuit.slimefun4.utils.holograms
This package contains a few utility classes that handle holograms in Slimefun.
io.github.thebusybiscuit.slimefun4.utils.itemstack  
Slimefun4 - Item Implementations 
Package Description
io.github.thebusybiscuit.slimefun4.implementation.items
This package contains the different classes for each SlimefunItem
io.github.thebusybiscuit.slimefun4.implementation.items.altar
This package holds the SlimefunItem implementations related to the AncientAltar.
io.github.thebusybiscuit.slimefun4.implementation.items.androids
This package holds implementations of SlimefunItem that are related to the ProgrammableAndroid.
io.github.thebusybiscuit.slimefun4.implementation.items.armor  
io.github.thebusybiscuit.slimefun4.implementation.items.blocks  
io.github.thebusybiscuit.slimefun4.implementation.items.cargo
This package provides the different implementations of SlimefunItem that are related to the CargoNet, most notably: Cargo Nodes.
io.github.thebusybiscuit.slimefun4.implementation.items.electric
This package contains the different implementations of SlimefunItem that also implement the interface EnergyNetComponent
io.github.thebusybiscuit.slimefun4.implementation.items.electric.gadgets
This package holds implementations of SlimefunItem that are used in combination with electricity, like the Multimeter or the SolarHelmet
io.github.thebusybiscuit.slimefun4.implementation.items.electric.generators
This package contains the different implementations of AGenerator.
io.github.thebusybiscuit.slimefun4.implementation.items.electric.machines  
io.github.thebusybiscuit.slimefun4.implementation.items.electric.reactors
This package contains the different implementations of AReactor.
io.github.thebusybiscuit.slimefun4.implementation.items.food
This package holds implementations of SlimefunItem that are related to food.
io.github.thebusybiscuit.slimefun4.implementation.items.geo
This package holds implementations of any SlimefunItem that deals with the GEOResource API.
io.github.thebusybiscuit.slimefun4.implementation.items.gps
This package holds implementations of SlimefunItem that are related to the GPSNetwork.
io.github.thebusybiscuit.slimefun4.implementation.items.magical
This package holds implementations of SlimefunItem that are considered magical items.
io.github.thebusybiscuit.slimefun4.implementation.items.medical
This package holds implementations of SlimefunItem that are related to healing yourself.
io.github.thebusybiscuit.slimefun4.implementation.items.multiblocks
This package contains all the different implementations of MultiBlockMachine
io.github.thebusybiscuit.slimefun4.implementation.items.tools
This package holds implementations of SlimefunItem that are tools.
io.github.thebusybiscuit.slimefun4.implementation.items.weapons
This package holds implementations of SlimefunItem that are weapons, implementations of SlimefunBow for example.
Slimefun4 - Old packages 
Package Description
me.mrCookieSlime.Slimefun  
me.mrCookieSlime.Slimefun.api  
me.mrCookieSlime.Slimefun.api.energy  
me.mrCookieSlime.Slimefun.api.inventory  
me.mrCookieSlime.Slimefun.api.item_transport  
me.mrCookieSlime.Slimefun.Lists  
me.mrCookieSlime.Slimefun.Objects  
me.mrCookieSlime.Slimefun.Objects.handlers  
me.mrCookieSlime.Slimefun.Objects.SlimefunItem  
me.mrCookieSlime.Slimefun.Objects.SlimefunItem.abstractItems  
me.mrCookieSlime.Slimefun.Objects.SlimefunItem.interfaces  
me.mrCookieSlime.Slimefun.Objects.SlimefunItem.multiblocks  
me.mrCookieSlime.Slimefun.Setup