CATs are tokens that you can create and/or trade on Chia's blockchain. The issuers of these tokens create the rules for their minting and retirement, using a "Token and Asset Issuance Limiter" (TAIL). The owners of these tokens have control over how they may be spent. CATs can be implemented as stable coins, stock issuance tokens, voting shares, or anything else you can think of. For more info, you can read about the nomenclature of CATs.