Rock and blues are two styles of music that can be easily confused to be the same, simply because both share certain similarities. Although the two styles of music were developed with the same instruments, such as drums, piano, electric bass guitar, organ, other instruments like trumpet, trombone, and saxophone are now being used when playing blues music. According to history, blues music was developed in the late 19th century and started from the southern part of the United States.
On the other hand, rock music started in the United States as well as in the United Kingdom in the 1950s. When you listen to blues, there are traces of Afro-American folk music, whereas rock shares more attributes with other genres of music such as electric blues, rock, and roll, etc. The simple twelve-bar blues is one of the common chords in blues, but pure rock uses 3 chords.