Four main types of Blues Music

Delta Blues-
The original type of blues music. Originally played by itinerant black men from the Mississippi delta region. Acoustic instrumentation as sparse as guitar and singer. Sometimes the group would include harmonica and piano. Features of the music include 12 bar arrangement and vocal repetition that frequently included a call and response lyrical framing. Artists that typify the style include: Charley Patton, Eddie J. "Son" House, Robert Johnson, and Muddy Waters.
Chicago Blues
Delta blues musicians brought their music north to the Chicago area. Muddy Waters was one of the first artists to use electric guitar to play his delta blues. Changes to the Delta blues style of playing included electric amplification of voice using microphones, addition of a drum set, horns, and most importantly, electric guitars. Artists that typify this style include: Muddy Waters, Willie Dixon and Howlin' Wolf.
Texas Blues
Similar to the Chicago blues. Included the same instrumentation as the Chicago style. Typified by artists like T-Bone Walker and Lightnin' Hopkins.
Blues Rock.
Originated in the early 1960's during the folk revival, this style of blues was directly influenced by the Delta and Chicago blues.
Young white musicians copied the lyrical styling and high energy of the earlier players, and cranked up both the volume and beat. Famous groups that typify this style include: The Rolling Stones, ZZ Top, the Doors and Credence Clearwater Revival.