Learn in the textbookThe OSI Reference Model and Its 7 Layers
DefinitionThe session layer (セション層) is Layer 5; it manages the whole exchange from the start of communication to its end, called a session (セション).
ExplanationIt sets up a session with the other party, places sync points along the way as checkpoints, and finally carries out the closing steps. Coordinating how the exchange proceeds, such as whose turn it is to send, is also this layer's job.
AnalogyIt is like a phone call: you say hello, confirm each point is settled, and say goodbye before hanging up.
Memory hookA session is one sitting of a meeting. Link it to the chair who runs the meeting from opening to close.