I'm looking to buy those plastic guards that are sometimes located under there front end of a car... WHATS THE TECHNICAL TERM FOR THEM

Are you asking about the 'Spoiler'?

Or are you asking about 'Splash Pan'?

Maybe even "Splash Guard"?

If you're referring to the pieces that go between the front bumper and the radiator support, some manufacturer's call these "close-out" panels or "filler" panels.
When calling for these, you can simply describe where they are and the parts professional should be able to either explain what it is you're looking for or if you're at the parts department, they can show you a picture.

Or "valance" or "front spoiler", "front air dam"