Delegation allows someone to lend someone Steam Power. Only the account whom gave it can take it back, or give it. It takes I think 7 days to get it back. I don't think there is a way to delegate yet from steemit.com. That requires still a command, blockchain interaction or something using the API (developer interface.) Scripts, apps and programs can use the API. Anyone could develop a tool to use delegation because the blockchain is open. Even add it to their own copy steemit.com's code (then request it to be added to the main copy.) There's also some other more intricate details I don't fully understand yet; as I just started studying Steem yesterday. LOL. Hope that helps you.