Concepts

Token-2022 extensions

Token-2022 is a newer token program with optional features baked into the mint. They must be chosen at creation time.

Transfer fee	A percentage of every transfer is withheld for the fee authority to collect.
Interest-bearing	The mint reports a continuously compounding balance for display purposes.
Non-transferable	Tokens can be burned but never moved — 'soulbound'.
Transfer hook	Every transfer calls a custom program. Powerful, and a risk to understand.
Metadata on mint	Name, symbol and URI live on the mint itself — no separate Metaplex account.

Before you choose Token-2022

Extensions can't be added after creation — decide up front.
Wallet and exchange support is good but not universal; some older tooling and a few CEXs lag.
If broad compatibility matters more than extensions, use the standard SPL creator.

Token Safety Check flags transfer-fee and transfer-hook extensions when it finds them on a mint.