What exactly is classical music, and what differentiates it from other musical genres?

Ah, that inevitable question. Labels can be problematic in any field; “classical music” especially so. One complication is that music history refers to the years from roughly 1750 to 1825 as the “classical” period, when Haydn, Mozart and Beethoven achieved their glory. But in a broader sense the term classical music has been adopted as a way to describe the continuing heritage of music mostly written to be performed in concert halls and opera houses by orchestras, singers, choruses, chamber ensembles and solo instrumentalists. Another characteristic is that composers in this tradition have been drawn to larger, structured forms. Still, the term is far from ideal, but no one has come up with a good alternative — yet.