What it is
Trumpets are the top voice of a salsa band's horn section, usually two or three. They don't play the whole song, only certain parts: the moña in the montuno and the arranged mambo.
The strokes
The trumpets play chord notes (root, third, fifth), short hits as a section, and the push — a chord on the & of 4 that pulls into the next bar.
What a dancer hears
The trumpets coming in signal that the song has moved to a new part. In the moña the trumpets and trombones trade phrases: the trumpets call in the first bar, the trombones answer in the second.
In the mambo the trumpets punch out the clave rhythm — a good moment for accents in the dance.