Home Assistant Basics: Entities, Devices & Integrations

You've installed Home Assistant (if not: pick the right variant here) and now face a UI full of terms. Before you build automations or dashboards, it's worth understanding the mental model behind it – it makes everything else logical.

Home Assistant organizes everything in a clear hierarchy:

Integration → Device → Entity, with the Area cutting across.

Understand these four and you understand Home Assistant.

An integration is the code that lets Home Assistant talk to a device, service or protocol – e.g. Zigbee (ZHA), MQTT, Hue, or the weather API. You add it once (“Settings → Devices & Services”); after that it brings its own devices.

A device is a concrete piece of hardware an integration discovered – say a Zigbee thermostat or a plug. It's mainly an organizational bracket: a device bundles several entities and can be assigned to an area.

The entity is the most important term. It's a single state or function: the temperature, the battery level, the on/off switch. A device often has several entities. Each has an entity_id in the pattern domain.name – the domain says what it is:

• sensor.living_room_temperature – a measured value
• light.desk – a switchable lamp
• binary_sensor.front_door – open/closed

An entity has a state (e.g. 21.4) and attributes (unit, brightness, …). These states are later the building blocks of your automations.

An area groups devices by room – “Living room”, “Office”. That later enables commands like “turn everything in the living room off” and sorts dashboards automatically. Optionally there are labels for cross-cuts (“all batteries”).

For devices and entities to exist at all, you need a source. In my setup a Zigbee coordinator on the server provides most of the sensors – a USB dongle bound in via an integration (ZHA or Zigbee2MQTT):

Concretely, top to bottom: the Zigbee dongle is bound in via the ZHA integration. You pair a thermostat – Home Assistant creates a device for it. That device brings several entities: sensor.thermostat_temperature, sensor.thermostat_battery, climate.thermostat. You put the device into the area “Living room” – done. From now on you can use the temperature entity in automations and dashboards.

• Helpers (input_boolean, counters, schedules) – your own “entities by hand”, relevant once you build automations.
• Templates – calculated entities; powerful, but not for the start.

Integration brings devices, devices bundle entities, areas sort by room – and the entity with its state is what you actually work with. With this model in mind, the next step is logical: your first automation made of trigger, condition and action. That's exactly what we'll build in the next article.