do brass instruments have keys or valves?

They have valves.

A brass instrument is a musical instrument whose sound is produced by sympathetic vibration of air in a tubular resonator in sympathy with the vibration of the player's lips. Brass instruments are also called labrosones, literally meaning "lip-vibrated instruments".[1]

There are several factors involved in producing different pitches on a brass instrument: One is alteration of the player's lip tension (or "embouchure"), and another is air flow. Also, slides (or valves) are used to change the length of the tubing, thus changing the harmonic series presented by the instrument to the player.

The view of most scholars (see organology) is that the term "brass instrument" should be defined by the way the sound is made, as above, and not by whether the instrument is actually made of brass. Thus, as exceptional cases one finds brass instruments made of wood like the alphorn, the cornett, and the serpent, while some woodwind instruments are made of brass, like the saxophone.

Keys are metal disks with pads (leather-covered, padded pieces) under them, which are pushed down to close a hole in a woodwind instrument.

Valves are just like hydraulic valves: they are mechanisms which move a piece (a piston or rotor) to change the direction of airflow through tubing.

Modern brass instruments use valves. They work by changing the length of the brass tubing (by switching in extra lengths) to change the pitch-length of the whole instrument.

There are two brass-mouthpiece instruments which survived far enough into the classical era that they are still used in modern performance, the Serpent and the ophicleide. (The former is shaped in s-curves, hence the name, the latter is a relative of the Russian Bassoon, which is also a brass-mouthpiece instrument.) These are keyed. One of the first efforts to use something other than a slide to change the pitch of a brass instrument (slides as in trombone) was called the "keyed bugle", because it had large keys on the sides of the conic-bore tubing. It isn't believed to have been a success, and isn't used today.

So, for modern instruments, brasses use valves, woodwinds use keys.

Brass instrument use valves, either piston or rotary. Piston valves, like those found on trumpets and most baritones/euphoniums, work by changing the shape of the horn by moving the valve up and down, therefore altering the direction of the airflow. Rotary valves, found on French horns and some trombones, work in the same way, just in a different direction- pressing the "key" turns a valve, changing the direction of the airflow parallel to the instrument. Rotary valves, however, are also called "keys" in many cases. Some rotary valve lubricants are labeled "Key Oil", and many times the part you press is called the key. Sorry to confuse the issue, but hope it answers your question.

Almost all brass instruments use valves.

Modern brass instruments use valves.

Both. The keys are used to move the valves. Trombones have neither.

we could see... Trumpet Trombone (undecided if it would be seen a valve device besides the certainty that it works a similar way basically you may desire to do the sliding your self.) French Horn Tuba and that i think of there is in all hazard one or 2 greater.

valves

They have Valves .

GO BAND!

Tthey have valves(: