Currency basics
Currency pairs are two countries' currencies combined to trade. The first currency of a currency pair is called the "base currency," and the second is called the "quote currency." Some examples of currency pairs include EURUSD, GBPJPY, NZDCAD, etc.
Bid price and ask price
Bid price: The price at which the base currency is bought by a broker and sold by a trader
Ask price: The price at which the base currency is sold by a broker and bought by a trader.
Balance,equity, and free margin
Balance is the calculated total of all completed transactions on a trading account, including deposits and withdrawals. It can be the amount of funds you have before opening orders or after closing all open orders; the balance does not change while orders are open.
Equity is the balance of a trading account plus or minus total rolling profit or loss and swap charges.
Equity = Balance +/- Floating Profit/Loss + Credit + Swaps