Two major mod foundations are used in modern Minecraft. There is the original: Forge, which has been the go to for many years now. There is also now, however, the Fabric mod loader, which is a much newer, and better-optimized way to play with mods.

Players can use either for the Create mod, as there is a version of the mod for each mod loader. So, they should simply go with their preference, or pick whichever loader has better compatibility with other mods that they wish to use.