The consumer or system UUID is a unique identifier used in the inventory subscription service. This UUID can be used to re-register the system if there is some kind of corruption or for internal tracking. In the GUI (Section 4.13.10.1, “Checking Facts from the Red Hat Subscription Manager UI”), this is listed as one of the system facts, under the system category:

From the command-line, use the identity command to return the current UUID. The UUID is the Current identity is value.

[root@server1 ~]# subscription-manager identity
Current identity is: 63701087-f625-4519-8ab2-633bb50cb261
name: server1.example.com
org name: 6340056
org id: 8a85f981302cbaf201302d89931e059a