In essence, pushing down valves makes the trumpet shorter or longer--at least, as far as air flow is concerned. This, of course, describes the basics. As any experienced player can tell you, actually playing a trumpet takes years to learn and perfect!
The trumpet is a very complex and difficult instrument to understand. The horns are brass and usually coated in a lacquer or silver plated finish.
Orchestral trumpet players are adept at transposing music at sight, frequently playing music written for the A, B ♭, D, E ♭, E, or F trumpet on the C trumpet or B ♭ trumpet.
There are already a couple of other good, accurate answers here, but neither of them delve very far into the specifics of playing the trumpet. Instead, the answers focus on physics instead of playing the horn. To understand how a trumpet works, st...
Compared to electric gadgetry, something like a trumpet is a pretty simple contraption, but the way it actually works is super clever when you see it in action.
Haydn's Trumpet Concerto, Hummel's Trumpet Concerto are two solos that are major works. Most composers from the classical era wrote concertos for most instruments at one time or another.
OK, in an extreme nutshell here is how a trumpet works. The lips are the vibrator that inputs acoustic energy in the horn. You close your lips up and then begin to increase the pressure in the oral cavity by blowing. When the pressure is high enough it blows the lips open inject a puff of air – a pulse – into the wind column, which is the horn.
The structure of the trumpet enables the note to be lowered by one tone by pressing the first valve, by a semitone by pressing the second valve, and by one and a half tones by pressing the third valve. The first valve lengthens the trumpet's tube by 160 mm, the second by 70 mm, and the third by 270 mm.