re: First Time Using Uber: It's basically a taxi service with a cool app

Yep. It just depends on what is available in your area at that time.

UberX seats 4 passengers. It is the least expensive Uber service. Uber X cars are cars like the Toyota Prius, Honda Accord. Known as UberPop in Europe
UberXL seats 6 passengers. UberXL cars are SUVs and minivans. XL costs more than UberX
UberSelect is Uber’s entry-level luxury service that seats up to 4 riders. Select cars are brands like BMW, Mercededs, Audi, etc with a leather interior.
UberPOOL: Share your Uber with another Uber user and split the cost. Read more about POOL.
UberBLACK and UberSUV is Uber’s luxury service. Commercially registered and insured livery vehicles, typically a black SUV or luxury sedan. Black is the most expensive Uber service