Or rather, what part do you not understand? DeFi is just people interacting with code rather than people, and with their funds being not held in custody; you should be able to get your money any time you want(unless stated otherwise, like with locked tokens, vesting, etc).
Also , what does the token has to do with it or is it unrelated at all??
It totally depends. Most DeFi platforms differ from each other. Mostly the tokens are for governance, sometimes for staking(revenue) rewards, etc.