CORA is the Common Registration API, and is the interface used by Client Automation to share computer registration data with other CA products (i.e. CA Service Desk Manager). Even if you're not integrating Client Automation with another CA product, the engines processing the collect tasks are still registering computers (and network adapters) with CORA during the processing of registration messages.
Coracleanup is a utility used to correct inconsistencies in the CORA database tables in the MDB. From the Client Automation product space, it does this by cleaning up all the existing computer (and network adapter) registrations from the CORA tables, then iterates through each Client Automation computer registration, and re-registers them with CORA, one by one. For each computer registration processed, the coracleanup utility also re-registers the list of network adapters associated with each computer.