Glossary
Fair value gap FVG
In short
A fair value gap is a three-candle pattern in which the wicks of the first and the third candle do not overlap. The gap between them marks an imbalance that price may come back to.

How it forms
The middle candle moves so fast that the first and the third candle leave a gap between their wicks. In that area, price only traded in one direction.
Filling the gap
When price trades back into the gap, it gets filled. AE Market Structure shows the fill level of each gap live, for example “40% filled”, so you see at a glance how much of it is left.