They help to keep the snow and ice from falling on your head when you slam the front door in a fit of rage because of the snow and ice.

They hold back snow and ice...a bit. When it does start to slide it breaks up the flow so you get 200 lbs of crap in bite size chunks instead of one giant bone crushing block.

They stop ice from freely sliding off.

Look like roof clips for snow if you're in that kind of climate

I am pretty sure they are called Rain Diverters.