Tournament Money (T-Money) is a balance you can use to enter tournaments without using your real money. You can only use T-Money for tournament buy-ins, not for cash games or withdrawals.
You can use T-Money to register for tournaments with a cash buy-in.
No, you cannot withdraw T-Money or exchange it for another currency. It can only be used to enter tournaments.
You can find your T-Money balance in the 'My Rewards' section.