If you are a music producer using a modern DAW (Digital Audio Workstation) like FL Studio, Ableton, or Logic, you might want to use these specific sounds without dealing with the high latency of the built-in Microsoft Synth.
But who plays the note? The computer needs a synthesizer. And to make that synthesizer sound like a trumpet rather than a flute, it needs a library of samples—a "bank" of sounds. windows default soundfont