Lawn Riding Mower - Difference Between Automatic and Hydrostatic

[unit731]

Up comes an Ariesn 22HP Intek V-Twin - 960460026 (the model number on back).
Used.
3 years old. Excellent condition.
A neighbor is moving and wishes to sell.

Apparently Ariens lawn/garden tractors are made by Husqvarna.

The sticker on side of machine states: Hydrostatic/Automatic.

Question:
Is there a difference between a Hydrostatic transmission and an automatic transmission in Lawn/garden tractors?
If so, what does this Ariens have?

 

[unit731]

I viewed this video on hydrostatic transmissions.
Interesting.

LINK