This is a view of the left side of the loom. 

arrow #1. The castle (maybe called the castle tower), which is the vertical structural element of the loom.

arrow #2. The beater. This is the mechanism used to 'beat' the weft into place to produce a nice tight weaving. The weft (also called 'filler') is the yarn that makes up the horizontal threads of the finished fabric.

arrow #3. The warp beam. This is where the warp is rolled up onto the loom. In this picture, the warp would be wound onto the left, threaded through the heddles and the reed and then attached to the cloth beam on the right. The warp is stretched tightly between the two beams, so that each warp thread has even tension (and there can be a lot of warp threads, hundreds usually). From what I understand, having even tension is a pretty important part of loom weaving, and not something easily done by the beginner. No one is a beginner forever, though. Also, the warp can be 'beamed' onto the loom from front to back or from back to front. There are advantages and disadvantages to each, but I don't really know what those are yet. I'm going to start front to back, because that's how the book I have describes the process. Also, back to front requires an extra (but easily made) piece of equipment called a raddle, which I don't have yet.