Globular clusters are composed of hundreds of thousands of very old stars, all tightly packed in a spherical area located near or in the halo of a galaxy.
M13 shown below is a great globular cluster easily visible in binoculars in the constellation of Hercules.
An Open cluster is composed of hundreds of stars born in the same molecular cloud about the same time.
This is the Pleiads Open star cluster M45. September, 2018