What is the difference between rock and classical music

Rock is a form of music that developed in the mid-1950s, largely influenced by rhythm and blues, country music and jingle-alley music.

Classical music is divided into two narrow and broad categories: narrowly defined as classical music, which was the dominant music of Europe during the period 1750-1820, and broadly defined as music created in the context of mainstream European culture from the Western Middle Ages to the present day, or music rooted in the Western tradition of liturgical and secular music, which covers the entire period from about the 11th century to the present day. It covers the entire period from about the 11th century to the present.

The two are very different in terms of instruments, orchestra, musical expression, and cultural background.