Glossary
Boost
In one line: Standing on a teammate's head to reach a high spot or see over cover.
What it means
In VALORANT you can stand on top of a crouching or standing teammate. A boost lets you reach spots you cannot get to alone, or peek over low cover for a moment and drop back down.
It is a surprise move: it works because nobody is aiming at that height. The weakness is that two players stand still in the same place, so one ability or one lucky shot can punish both. Use it rarely and for a clear reason.
An example
On a site with boxes, your teammate stops next to a crate and you jump on their head: from up there you see a defender hiding behind it and catch them off guard. Then you move at once, because now everyone knows where you are.