Session Description Protocol (SDP) is a text-based format used to describe multimedia sessions, providing technical specifications required for setting up real-time services like video conferencing and VoIP calls. It streamlines the process of setting up multimedia sessions by introducing a universal format that outlines attributes and parameters such as media types, codecs, IP addresses, and port numbers. SDP is often used in conjunction with other protocols like SIP (Session Initiation Protocol) to initiate, maintain, and terminate multimedia sessions.