> ## Documentation Index > Fetch the complete documentation index at: https://docs.talqui.chat/llms.txt > Use this file to discover all available pages before exploring further. # Sessions ## Overview In Talqui, a **Session** is the conversation entity that relates a single **Contact** to the messages exchanged with a tenant through a specific channel. It is the object that keeps the context of an active conversation, including channel identity, ownership flow, timestamps, and the set of messages that belong to that interaction. A single contact can have **many Sessions** over time, and each Session can contain **many Messages**. In practice, every active conversation in Talqui is represented by one session. When that interaction ends and a new conversational window starts later, Talqui may create a new session to represent that new conversation lifecycle. For developers, Sessions are important because they are one of the main integration points of the platform. Your application can read session data, react to session-related events, and create new sessions through the REST API when an external system needs to open a conversation with one specific contact. Sessions and Campaigns solve different problems. Use **Campaigns** when you need batch or mass sends, usually with the same content or the same approved model distributed to many recipients. Use **Sessions** when you need a **one-to-one conversational interaction**, typically triggered by an operational event such as an order update, a support action, an account notification, or any other transactional workflow initiated by your backend. *** ## Session Start Talqui exposes a `Session Start` mechanic for integrations that need to open a conversation from an external API call. The exact request shape depends on the channel and on the plugin installed in the tenant, because some channels allow free-form outbound messages while others require pre-approved models or marketplace-specific addressing rules. The guides below explain the most common Session Start mechanics currently used in Talqui. Understand the international phone number pattern expected by Talqui endpoints. Learn how to open conversations through the Sessions endpoint. This documentation is built and hosted on [Mintlify](https://mintlify.com), a developer documentation platform.