Ward:

A ward is a placeable vision object in Dota 2 that gives a team information about nearby areas of the map. Wards are used to scout enemy movement, protect objectives, and improve map control by revealing safe or dangerous zones.

Warding is a core part of support play because good ward placement can prevent ganks, set up ambushes, and help a team take fights with better information. Wards are usually paired with sentries or dewarding to remove enemy vision.