> ## Documentation Index
> Fetch the complete documentation index at: https://docs.xo.market/llms.txt
> Use this file to discover all available pages before exploring further.

# Markets, events and series

> How Series, Events and Markets relate — and which mechanism a market uses.

XO groups related questions without changing what you actually trade.

| Level      | What it is                                                                                                                       |
| ---------- | -------------------------------------------------------------------------------------------------------------------------------- |
| **Series** | An optional collection of related events.                                                                                        |
| **Event**  | The topic page and rules context. An event can contain markets directly, or use one level of sub-events before the market lines. |
| **Market** | One tradable condition, with its own outcome tokens and its own settlement rules.                                                |

The market is the unit that settles. Two market lines under the same event are separate conditions — separate rules, separate books, separate outcomes — even when they share a topic page.

## Two trading mechanisms

XO currently exposes both an order book and a legacy automated market maker. Which one you get depends on the market.

|               | Order book (CLOB)                           | Legacy AMM                |
| ------------- | ------------------------------------------- | ------------------------- |
| Counterparty  | Other traders' resting orders               | A pricing pool            |
| Route         | `/event/[slug]`                             | `/markets/[slug]`         |
| Limit orders  | Yes                                         | No                        |
| Visible depth | Yes                                         | No                        |
| Quote shows   | Book depth, average price, protection price | Price impact and slippage |

Market cards label the mechanism. Check it before opening a market — the controls available to you differ. See [Place an order](/product/trading/place-an-order) and [Legacy AMM markets](/product/trading/legacy-amm).

## Market states

| State    | What it means for you                                                                                              |
| -------- | ------------------------------------------------------------------------------------------------------------------ |
| Active   | Trading is open.                                                                                                   |
| Paused   | New orders are rejected. Existing resting orders are retained and the market can return to Active.                 |
| Resolved | Terminal. An outcome was recorded; resting orders are cancelled; winning positions can become claimable.           |
| Voided   | Terminal. The market was invalidated under its published rules; eligible positions follow the defined refund path. |
| Closed   | Terminal. The market ended without a resolution under engine rules.                                                |

Integrators can read the same lifecycle from the API side in [Market lifecycle](/guides/market-lifecycle).