M 13 is one of the most splendid globular clusters in the northern hemisphere, containing several hundred thousands of stars. Globular clusters are very old objects, almost as old as the universe. They mostly contain old, reddish stars, but also a few hot, blue 'straggler stars', which appear to be much younger. They probably were generated by collisions of two older stars or through mass transfer between partners in a binary star system, 'rejuvenating' the resulting blue star.
The galaxy near the upper left corner is NGC 6207.