An okay trade
I sold 15,000 euro against US dollars at 15:39 (the yellow triangle) and bought it back at 15:55 (the second green dot), making $47.25 plus $0.0039 of interest.
The profit here was 31.5 pips. A pip is normally the smallest movement a currency can make; in EURUSD, a pip is one ten-thousandth of a dollar. (Units smaller than a pip are typically called "pipettes".) My total profit is the pip size multiplied by the size of the position, plus any interest paid or received. Good technical traders can have hundreds or even thousands of pips of profit during a week. Or lose just as much.
In this position where I was short euros, the interest I paid borrowing euro was lower than the interest I earned on my dollars. This is why I earned interest on my position.