A session is a bounded period of two-way conversation between a customer and an agent, used by some platforms for pricing and by analytics to group messages into one interaction.
Sessions in pricing
Outside the US, carriers price RCS by conversation: one fee opens a window, typically 24 hours, during which further messages in that thread are included. US carriers now offer the same for senders registered as conversational: once 4 messages are exchanged within 24 hours, at least 2 of them from the customer, one session charge covers every message in that window, Rich Media included; other senders are billed per message. The two models suit different traffic: a chatbot exchange of thirty short turns is cheaper as a session, a single reminder per message. On SimplyRCS this is called conversation pricing: $0.05 per conversation plus the carrier's conversation fee; How RCS billing works compares the two with worked examples.
Sessions in analytics
Independent of billing, platforms group messages into sessions to answer questions like "how many turns did it take to resolve" or "what share of conversations ended in a booking". A session usually starts with a mobile originated message or an agent message and closes after a period of inactivity.
What a session is not
It is not a consent window. A customer's consent governs whether a business may message at all and does not expire with a session; a STOP ends the relationship, not the conversation.