mSATA SSD--what is it & what's it for?

I'm new to PC building, and I just found this stuff called mSATA SSD. The problem is I don't know what it does or how it works. I also can't find anything online as to what they do or how they work. I hope to find some help here. Thanks in advance.

from what I know, mSATA is available on your MOBO, basiccly it's a slot on your motherboard, that allowes you to put a small SSD without taking up much space in your case. Or using a 32GB mSATA SSD for boot.

Thanks. Anyone else? Or is this really all it is?

it's a small ssd (phisically, they go up to 240gb), that goes into your motherboard, i don't think it's quite as fast as sata3, but it's nice for saving space and it could be handy for a ssd boot drive

many ultabooks use them like surface and macbook air (yes i know niether of them are actually ultrabooks)

they are a small form factor SSD, they actually go up to 480 and 512GB but whatever, they are useful for laptops, especially thin ones, and on small form factor desktops and HTPCs builds for example they are super conveinent in this "case mod"

https://www.youtube.com/watch?v=cBtYiQ1mnvA