# Concepts

Understand how ATLAS works before you follow a guide. For step-by-step tasks, see the [guides](https://docs.atlas.ilionx.dev/guides.md). For lookup facts, see the [reference](https://docs.atlas.ilionx.dev/reference.md).

| Page                                            | What you will learn                                                               |
| ----------------------------------------------- | --------------------------------------------------------------------------------- |
| [Why ATLAS](https://docs.atlas.ilionx.dev/concepts/why-atlas.md)                       | The problem ATLAS solves, and how it handles spend, data, providers and security. |
| [Organisations](https://docs.atlas.ilionx.dev/concepts/organisations.md)               | Your tenant: people, roles, sign-in and contract.                                 |
| [Spaces](https://docs.atlas.ilionx.dev/concepts/spaces.md)                             | The hierarchy that carries shared rules and budgets down to teams.                |
| [Projects](https://docs.atlas.ilionx.dev/concepts/projects.md)                         | A home for one AI deployment, with its own keys, models and funding.              |
| [API keys](https://docs.atlas.ilionx.dev/concepts/api-keys.md)                         | How a key identifies a caller and decides what a request is charged to.           |
| [Providers and models](https://docs.atlas.ilionx.dev/concepts/providers-and-models.md) | The AI services you connect, and the priced models you offer from them.           |
| [Gateway](https://docs.atlas.ilionx.dev/concepts/gateway.md)                           | The single endpoint your tools call, and what it does for every request.          |
| [Budget and cost](https://docs.atlas.ilionx.dev/concepts/budget-and-cost.md)           | How requests are priced, capped before they happen and invoiced.                  |
| [Usage and audit](https://docs.atlas.ilionx.dev/concepts/usage-and-audit.md)           | The record behind usage statistics, audit search and data privacy.                |
| [Identity and access](https://docs.atlas.ilionx.dev/concepts/identity-and-access.md)   | Single sign-on, roles, suspension and automatic provisioning.                     |