The Session Description Protocol (SDP) is a format used for describing multimedia communication sessions. It provides essential information about the session, such as the media types, codecs, and network information needed for participants to connect and communicate effectively. SDP is commonly used in protocols like Session Initiation Protocol (SIP) and Real-time Transport Protocol (RTP). SDP is typically included in the signaling messages exchanged between devices, allowing them to negotiate session parameters. This ensures that all parties involved in a communication session can understand and agree on how to transmit audio, video, or other data types, facilitating seamless interaction.