Do I have the "gist" of buying lights correct?
 

The physical light itself is the same for the key, fill, back...but it is fitted with different accessories and the intensity of the bulb is lowered/increased?

As you can see I am lost when it comes to lighting...I am predominantly a outdoors and natural light shooter. If I ever need lights in the past I had a basic on camera setup. However, I am gearing up to shoot a video in front of a white backdrop and don't know exactly what to purchase (or rent in my case).

This should help:

Lowel EDU - a Lighting Resource Center

Go through the foundations and then the lessons. When you finish that, you'll know enough about lights to feel very comfortable buying, renting, and arranging your setups for most kinds of shots.

a grey backdrop :-)
you know many "white" things on video that we see are not nessisarily Stark 100% white, the movie and video people will use an 80% white as white, so it doesnt blow out everything else.
i cant think of anything i would less want to have as a backdrop , but if White is the need, and it is toned down a bit with either the lighting or the backdrop itself (better) then you will get your stark white still, without having a Fight White on your hands that the video camera cant deal with due to its limited contrast range.

Wouldn't I want to light the backdrop more than the subject to get it to be as white as possible with no sight of imperfections?

surely you can test this in 2 seconds with ANY video camera or even a digital still camera, just hang up a white sheet, and put someone in front of it, then take a shot, you will observe what happens so fast, you wont need to ask.