Stun:

A stun is a disable that prevents a unit from acting normally for a short time, usually by stopping movement and the use of abilities or items. In Dota 2, stuns are a common tool for starting fights, setting up kills, interrupting channeling spells, and locking down key targets during a team fight.

Because stuns can interrupt escape attempts and channeled abilities, they are often chained with other disables to keep an enemy out of the fight for longer.