What is 'Credit' and can I use it to trade?

Credit is a separate wallet that holds bonus funds, chiefly the one-time welcome bonus you receive when you reach a membership tier. It behaves differently from your Balance: Credit can support your trading — for margin and account equity purposes your equity is Balance plus Credit, so it gives your positions more cushion — but Credit is not withdrawable and does not count toward the lifetime-deposit total that determines your membership tier. Realized trading profits are booked to your real (withdrawable) Balance, while the Credit itself stays as bonus funds. In short: use Credit to trade with more room, but only your Balance can be cashed out to your wallet.