Lovely blues song here. This one is a classic blues tune that has been covered by many artists. This is one of the most well known versions, played by Fleetwood Mac with Peter Green on lead (Although here we just see the backing chords for the song).

It's a blues progression in A using 7th chords. Here's the main progression:

A major - A7 - D7 - D# dim - A major - F#7 - Bm7 - E7 - A major - D9 - A major - E7

A few times he uses different chord variations to end the sequence, but it's basically the same progression throughout. Then, in the middle section of the song, there is a second type of progression which uses the following chords:

D7 - D# dim - A7 - A9 - B7 - E7 - F7 - E7

Then return to the first progression again until the end of the song.

This is a great backing track for practicing your blues solos with. You can use a wide variety of scales here: A major, A mixolydian, A dorian, A blues scale, A minor scale to name but a few. Because of the backing chords you sometimes need to be careful about which notes to hang on, but there's also a lot of scope to include irregular scale notes for nice bluesy bends and licks!