Glossary

Automation:
Capability to call a service based on a simple or complex trigger. Automation allows a condition such as sunset to cause an event, such as a light turning on.
Component:
The components provide the core logic for the functionality in Home Assistant. Like notify provides sending notifications.
Device:
Usually this is a physical unit which can do or observe something.
Discovery:
The automatic setup of zeroconf/mDNS and uPnP devices after they are discovered.
Entity:
An entity is the representation of a single device, unit or web service.
Event:
When somethings happen.
Groups:
Groups are a way to organize your entities into a single unit.
Platform:
A platform makes the connection to a specific software or hardware platform. The pushbullet platform works with the service from pushbullet.com.
Service:
Services are called to perform actions.
Template:
An automation definition can include variables for the service or data from the trigger values. This allows automations to generate dynamic actions.
Trigger:
Values or conditions of a platform that are defined to cause an automation to run.
hass:
Often used abbreviation for Home Assistant.