When you create a new workspace you have different workspace types and each type is for a specific thing.
Minecraft Forge mod
A workspace with this type is something called a ”mod”. In Minecraft, a mod (or modification) is a file added to the game with an API (in this workspace type, it is Forge) to add new elements to the game that needs to be coded with Java. This workspace type is the first workspace type that MCreator has added, and it is the main workspace type of MCreator. You will have the possibility to use everything inside the software.
Data Pack
A Data Pack is another workspace type to customize the game of the player in adding the possibility to create or change new advancements, functions, loot tables, structures, recipes, or tags. The Data Packs don’t use Java, but only JSON files. They have added in 1.13.
Add-On
An add-on is something like the mods of the Java Edition, but they are for the Bedrock Edition (IOS, Android, Windows 10 Edition, Xbox, etc.). It means you can add the same elements as with Forge mods. However, as the developers of the Bedrock Edition are still working on this feature, they are not fully implemented inside MCreator.
Other workspace types
If you have a plugin adding a new generator supported (like the Fabric Generator or Spigot generator), you will see it on the list.
Fabric Minecraft mods
MCreator inherently only supports Minecraft Forge mods, Add-Ons, and data packs at the time of writing. However, more generator types are supported in MCreator's generator core and can be exposed using plugins.
Fabric is a modding framework for Minecraft. It is described as a lightweight and modular open-source modding toolchain.
Read more on about How to make Minecraft Fabric mod with MCreator by clicking on the link.
Spigot Minecraft server plugins
MCreator inherently only supports Minecraft Forge mods, Add-Ons, and data packs at the time of writing. However, more generator types are supported in MCreator's generator core and can be exposed using plugins.
SpigotMC is a server plugin frameworks for Minecraft servers.
Read more on about How to make Spigot Minecraft server plugin with MCreator by clicking on the link.