I'm going to have to take a crash course on what the heck to call them, splitter(s), skirts, spoilers etc.
Anything around the bottom edge of the car falls under the umbrella term "ground effects." The ultimate goal of anything like this is to create a downforce to enable the car to increase the available friction between the tires and the ground during high-speed cornering and to add stability while travelling at high speeds in a straight line. The secondary purpose is to control how the air moves around the car to dynamically improve cooling and to reduce drag, which is much more advanced than slapping items around the edges of the car.
The three main front and rear components used are splitters, spoilers and wings.
Splitters are, as mentioned above, installed on the front of the car. This can be classified as 'ground effects'. It is a flat piece of material that extends horizontally out from the bottom edge of the car. They can be small...
The black thingy under the chin of the front bumper.
... or large.
That giant table on the front.
Next is a spoiler. This can be installed on the front or back of the car. On the front, they are a ground-effect because they involve the air around the bottom of the car. On the rear, they are not. It is a vertically-mounted flate plane that does exactly as the name says: it 'spoils' the air, often in areas where turbulent air collects. This created a pressure differential that produces downforce. On the front, it is also called an 'air dam'. Those platic/rubber bits that extend beyond the bottom of your front bumper, way back from the front of your economy car? Those are spoilers.
Front:
Rear:
Wings are the final major component. They are not a 'ground effect' item as they are usually not against the lower edge of the car. These mostly for downforce and are held away from the body on supports in order to be exposed to cleaner moving air, allowing for a greater potential downforce. They can be mounted on the front or rear of the car, but is often only found on the rear of closed-wheel cars.
Rear:
Front:
(Yes this is for real. Yes, this is a Nissan GTR).
Lastly, the bits that extend along the length of the sides of the car. These are the side skirts, often called rockers (incorrectly as a rocker is an integral part of he structure of the car). They can extend horizontally away from the car or vertically down, towards the ground. They prevent air flowing along the edge of the car from traveling underneath the car.
There's a lot more to it than that, but those are the basics.