Realized Profit
Realized profit is the amount of money you made when you closed a winning trade.
For example, say you took a long position on ETH (you bought ETH) at $200 with $1000 (you have 5 ETH), and the price went up to $250 and you sold. Your realized profit would be $250: ($250 - $200) * 5.
Once you've realized profits, you can now use that money to make other trades, or to buy a lambo in celebration.