What does the SIP method "INVITE" accomplish?

The SIP method "INVITE" is primarily used to initiate a call or session between users in a VoIP (Voice over Internet Protocol) environment. When a user wants to start a communication, the SIP INVITE message is sent to the intended recipient. This message contains information about the session that is being proposed, including codecs, media types, and session descriptions. Upon receipt of the INVITE, the recipient can accept or reject the session, leading to the establishment of a media session if accepted. This process is the foundation of initiating voice or video calls in SIP-based communications, making it a crucial component of the SIP protocol.