I've got rhythm, I've got youtube, I've got Gershwin, who could ask for anything more?

So this is George Gershwin in 1933, despite the date on the clip. I'm hoping you've heard his name before. He is one of America's greatest composers. Some of his masterpieces are "Rhapsody in Blue", "Porgy and Bess", and "I've Got Rhythm", which is shown here. In jazz, the most common tune to solo on is a 12 bar blues, the second most common tune is Rhythm Changes.

Rhythm Changes are the chord changes to "I've Got Rhythm". So you see it's all pretty simple. The primary chord sequence for the A section of Rhythm Changes is I - VI - II - V. You will see that little pattern all over the place in jazz, so should try and become familiar with the sound of that. The bridge is moves around the circle of fifths and then goes back to the pattern. So in the key of C the bridge would be E7 to A7 to D7 to G7 and back to C. There are a a myriad of songs written over these changes, and "I've Got Rhythm" is a good one to start with. This is a good head to memorize and try in different keys.