To make sure there are no "fake" orders on the order book, Liquid will lock a part of your balance when you place a limit order that is not matched and filled immediately.
For example: Your total balance is 2 BTC. You place a limit order selling 1 BTC. As long as order remains live and unmatched and you don't have any other live orders, your free balance is (2 - 1) = 1 BTC.
Used margin, unrealized PNL, live loan offers, and pending withdrawals all have the same effect on your free balance ("Available Balance").
To summarize, Available Balance is the remaining of your Total Balance of one currency, after deducting:
- Order margin (value of all unfilled live orders of the same currency)
- Used margin of open positions that uses this currency as funding
- Live loan offers
- Absolute value of all unrealized PNL