The Fabric API is an API used by Fabric mods to interact better with vanilla Minecraft. It is required by most but not all Fabric mods in the mods folder.
Fabric API · Exposing functionality that is useful but difficult to access for many mods such as particles, biomes and dimensions · Adding events, hooks and APIs ...
design · Fabric's APIs are lightweight and modular, making porting faster and game instances leaner. · Fabric development targets snapshots as well as release ...