Multivibrators are important circuits used two generate two state signals like square wave, etc.
Depending on the number of stable states, the multivibrators can be divided into 3 types.
1) Astable Multivibrator
2) Monostable Multivibrator
3) Bistable Multivibrator
In this video, the multivibrator and types of multivibrators (Astable, Monostable and Bistable Multivibrator) are explained briefly.