OpenStack is a modular cloud operating system, composed of drop-in projects, each of which adds a specific feature set. Charmed OpenStack refers to the manner in which OpenStack is deployed and managed: with Juju charms.
Ceph is a standard component of Charmed OpenStack. It typically acts as backing storage for multiple OpenStack projects such as Cinder, Nova, Glance, and can provide a Swift-compatible API via the Ceph RADOS Gateway. The charms will create a specific Ceph pool for each such backed service.
OpenStack integration with Charmed Ceph is documented in the OpenStack Charm Guide.