JCR – Java specification for accessing a content repository, CQ5 uses its own implementation of JCR called CRX. Apache Jackrabbit is an open-source implementation of JCR 2.0 specification.
Apache Sling – RESTful framework to access a JCR over http protocol. It maps the REQUEST url to the NODE in JCR.
OSGI – framework for modular application development using java. Each module called bundle can be independently started and stopped.