A trumpet has three valves that let you play an entire chromatic scale on the instrument. A bugle has no valves and is a single continuous spiraling tube. Bugles can only play in a particular key and are typically pitched in C, F, G, or B♭.  Bugles are traditionally used for military drills and battle calls. The extra valves on a trumpet make the instrument heavier and more prone to sticking and damage than the simpler bugle.