How does the UnitStep function works?

I’m just started to use Mathematica. I have been going through various demonstration files, and have so far didn’t understand the language really
I just discovered the UnitStep function.

For me it looks like the step is always made on were x is zero.

How can I change the function that the step is made at another x value?

Cheers Chris

You are probably going to kick yourself when you see this:

Plot[UnitStep[x - 2], {x, -3, 3}]