Which protocol is called push protocol?

Excuse me, but I'm curious about a specific term in the realm of cryptography and digital communication. Could you please clarify which protocol is commonly referred to as the "push protocol"? I'm interested in understanding its purpose, functionality, and how it differs from other protocols in the field. Additionally, if there are any notable examples or use cases of the push protocol in practical applications, I would greatly appreciate if you could elaborate on those as well. Thank you in advance for your insight.