# Sites & Data

The V2 API consists of three building blocks that build on each other. You configure a
**site** once and then query it for forecasts and historical data.

## The three building blocks

### [Sites & Strings](/en/v2/api/sites)

A **site** describes your PV system: coordinates, one or more PV strings
(orientation, tilt, power) and optional configuration (module technology, shading,
inverter, tracker). Elevation, timezone and horizon shading are determined automatically.

### [Forecasts](/en/v2/api/forecast)

A PV power forecast for a site — by default just the power (`pv_power`),
optionally with weather, irradiance, clear-sky reference, per-string values and a
variability band.

### [Historical Data](/en/v2/api/historical)

Past PV yields and weather data over freely selectable time ranges — as a rolling window
(`period`) or with a fixed start/end date.

:::tip
You'll find the complete endpoint, parameter and field reference in the **[API Reference](/api)**.
:::

## Authentication

All V2 endpoints use bearer token authentication:

```bash
Authorization: Bearer YOUR_API_KEY
```