What is the significance of "Priority" field in Concurrent Program Definition??

Oracle definition for Priority: 
Priority is used to indicate the priority that the concurrent request will be assigned when it is submitted. If you do not assign a priority, the user’s profile option Concurrent:Priority sets the request’s priority at submission.
To Know how to set the priority, read this article: http://www.oracleappshub.com/aol/priority-for-concurrent-program/