Globular clusters are usually very old, whereas open clusters are generally quite young. Well, that's as you would expect. In globular clusters the stars are quite densely packed together, so their gravity holds them together for billions of years. In open clusters, on the other hand, the stars are further apart and so gradually drift apart over the eons. Our own Sun was probably formed in a stellar nursery like M42 (Great Orion Nebula), but it has long since lost contact with its sister stars.
So how is it that M67 in Cancer, NGC 188 in Cepheus and NGC 6791 in Lyra are still around after about 4, 5 and 8 billion years respectively?
(Wouldn't it be cool if the Sun was still part of a cluster? Imagine what the night sky would look like!)