It evolved in the 1940's and 1950's. Heavily influenced by rhythm and blues, blues, country music. It centers in electric guitar -- with electric bass and drums. Usually a 4/4 time signature using verse-chorus form. It places a higher degree of emphasis on musicianship and live performances than pop music.

Sub genres? Can I just give 10?
1. Punk Rock
2. Psychedelic Rock
3. Italian Occult Psychedelia
4. Glam Rock
5. Gypsy Punk
6. Gore Grind
7. Death 'n' Roll
8. Dark Cabaret
9. Christian Rock
10. Acid Rock

And if you're confused with rock and metal, metal revolves around a dark theme. Usually having its lyrics talking about depression, death, violence, sex, drugs, etc. It has highly amplified distortions and rapid guitar solos -- guitar shreds, I mean.

Hope this helps.
If you're interested with this types of music genres, talk to me. This is my forte -- lol. Who knows, I might teach you outta this world guitar shreds. :)