There are two types of margin: "used" and "free." In one of our last sessions, we looked at the Used Margin, which is the sum of all the Required Margin from all open positions. The gap between Equity and Used Margin is called Free Margin.
Account equity also called equity by some people represent the current worth of your trading account.
To understand what is used margin, it is also useful to understand what Required Margin is. Required Margin is the portion or part of margin needed to open your trade.
You have to learn the lingo, just as you have to master any new skill ...... In other words, it's like trying to win the heart of your lover.