There is a slight difference between receiving a denial versus a rejection. A denial occurs when  you’ve submitted your application, it is accepted for review and is reviewed by the Immigration Officer. After they’ve completed the review they deny your application request for a one or more reasons.
A rejection can occur when you’ve submitted your application and upon submission the Officer rejects it and returns it to you. This happens when your application is incomplete. Some examples of this include when you are missing supporting documents, signatures are not in the format required, original documents are not available.