Light switch sizzled
Shoot photos of the wiring and let us walk you through it.  

The usual place people get derailed is in 3-way switches; they count on the screw positions or wire colors meaning anything at all.  The screw positions vary on every switch, and the colors are worse than random in 3-ways. I even recommend you mark the travelers with yellow tape; doing so makes things easy. 

Even on a 2-way you sometimes see more than 2 non-ground wires; almost always two always-hot wires  and the installer just used the switch terminals as a lazy way to splice them.  More logical is a pigtail; but a novice switch replacer usually does not have the supply of wire,  wire-nuts and stripper needed to do a pigtail. 

But the #1 complication is dumbth; people not being conscious that they have outranged their skills and thinking they can just blunder about and get lucky. It's less of a risk on switches, but on other things, experientation can lead to many combinations that work but kill you later.  Skills are so easy to acquire that I advise to do so.