What is this thing called on the motherboard PCB?

[thetester]

Sorry if this is wrong place to post. But I just needed to know what this thing is. It's on every motherboard that I have seen. I'm not really a PCB expert or anything but I just want to know. (I'm not trying to fix it or anything) Also it would be nice to know what it does. Thanks for the help.

I circled it.

 

[Onus]

It looks to me like the clock crystal.