Watch the Confusing Terms online guitar lesson by Jeff Scheetz from Street Theory for Guitarists
One of the stumbling blocks to learning guitar theory, and just learning guitar in general, is the fact that often times the same thing can have several different names. Different instructors refer to exactly the same thing with completely different terms, and that can get confusing.
Theory has a certain air about it - that is all set in stone and absolute. But just keep in mind that's not always the case; there can be many ways to look at certain aspects of theory depending on how you are using it, and some things are referred to with different terms.