# Glossary (/docs/reference/glossary)



| Term                                                                      | Meaning                                                                                                                                   |
| ------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------- |
| <span id="agent">**Agent**</span>                                         | A definition: id, instructions, tools, and capabilities. See [Build](/docs/build).                                                        |
| <span id="app-server">**App server**</span>                               | Your server that signs people in, holds the Tenant key, and calls the Runtime for each person. See [App server](/docs/deploy/app-server). |
| <span id="capability">**Capability**</span>                               | A named bundle of instructions, tools, and hooks attached with `.use()`.                                                                  |
| <span id="durable-streams">**Durable Streams**</span>                     | S2 event history and live session streams.                                                                                                |
| <span id="durable-session-execution">**Durable Session Execution**</span> | Restate-backed wakes and serialized session advancement.                                                                                  |
| <span id="executor">**Executor**</span>                                   | Your process that runs tools, hooks, workflow functions, and verification nodes. See [Executors](/docs/run/executors).                    |
| <span id="host-root">**Host root**</span>                                 | `NYLORUN_HOME` or `~/.nylorun`: Host identity, credentials, stack files, and Tenant files.                                                |
| <span id="project">**Project**</span>                                     | Your application. See [Your project](/docs/project).                                                                                      |
| <span id="project-link">**Project link**</span>                           | `.nylorun/link.json` and `credentials.json`, connecting a Project to a Tenant.                                                            |
| <span id="runtime">**Runtime**</span>                                     | The service that runs sessions, calls the model, and stores history. Also called the Runtime Host.                                        |
| <span id="scope">**Scope**</span>                                         | What a subject may do, e.g. `sessions:own`. See [as()](/docs/reference/agents/client#as).                                                 |
| <span id="session">**Session**</span>                                     | One durable conversation or workflow run inside a Tenant. See [Sessions](/docs/run/sessions).                                             |
| <span id="session-store">**Session Store**</span>                         | Postgres state for sessions, checkpoints, effects, and definitions.                                                                       |
| <span id="studio">**Studio**</span>                                       | The local dashboard. See [Studio](/docs/studio).                                                                                          |
| <span id="studio-principal">**Studio principal**</span>                   | Per-Tenant credential Studio derives from the Host admin key.                                                                             |
| <span id="subject">**Subject**</span>                                     | The person an app server calls the Runtime for, sent as `Nylorun-Subject`.                                                                |
| <span id="tenant">**Tenant**</span>                                       | An isolated Postgres schema, S2 basin, Host directory, vault, principals, and sandboxes.                                                  |
| <span id="turn">**Turn**</span>                                           | One input and everything the agent does until it completes, pauses, fails, or is cancelled.                                               |
| <span id="workflow">**Workflow**</span>                                   | A runnable graph built from Loop, Chain, Switch, Map, and Parallel. See [Workflows](/docs/build/workflows).                               |