# Key concepts > For the complete documentation index, see [llms.txt](https://www.jetbrains.com/help/air/llms.txt). This topic defines the terms used across the Air in IDEs documentation. Agent : A coding agent that Air in IDEs can run, such as Codex, Junie, or another supported agent. An agent can come from a local installation on your machine or from the agent registry. Session : A session is one conversation with an agent. It includes the conversation history, attached context, and the process Air in IDEs uses to run the agent while the session is active. : : : : Refer to [Agent Session View overview](air-in-ides-interact-with-the-agent.html#agent-session-view) for details. Authorization source : The account or credentials that an agent uses during a session: the login that the agent manages itself, JetBrains AI, or a provider configured in Air in IDEs. : : : : Refer to [Configure agent authorization](air-in-ides-authorization.html) for details. Context : Project information that you attach to a request or session, such as files, commits, or a skill. Context gives the agent the information it needs to work with the same project or data that you see in the IDE. : : : : Refer to [Attach context](air-in-ides-interact-with-the-agent.html#prompt-context-attachments) for details. Preset : A named, reusable configuration that specifies the agent, model, effort, and access level for a session. : : : : Refer to [Create a custom preset](air-in-ides-presets.html#launch-profiles) for details. ACP agent : An agent that communicates with Air in IDEs through the [Agent Client Protocol (ACP)](https://agentclientprotocol.com/overview/introduction). ACP standardizes communication between code editors or IDEs and coding agents. : : : : Air in IDEs displays an ACP agent's progress, tool calls, permission requests, and forms in a structured interface instead of plain text. CLI agent : An agent that Air in IDEs runs as a command-line tool. Air in IDEs displays a CLI agent in a terminal interface rather than a structured interface. Surface : The interface in which a session runs: a chat in the IDE for an ACP agent, or a terminal in a full-screen editor tab for a CLI agent. MCP : The [Model Context : Protocol](https://modelcontextprotocol.io/docs/2026-07-28/getting-started/intro). Air in IDEs uses MCP to provide supported agents with different tools, extending their capabilities. Skill : A set of instructions that tells an agent how to perform a specific kind of task. You can attach a skill to a request as part of its context. ## See also ### External Links [Agent Client Protocol](https://agentclientprotocol.com/overview/introduction) [Model Context Protocol](https://modelcontextprotocol.io/docs/2026-07-28/getting-started/intro)