The easiest thing for you to do is to look up the definitions for these terms in the PMBOK Guide glossary starting on page 526 of the 5th edition.
On a very high level: Activity List and Activity Attributes focus on your schedule activities (on the "tasks") while the WBS Dictionary focuses on describing your deliverables (the "scope").
And yes... as you make your way through the various lessons of The PM PrepCast you will come across these again and again. The terms may be confusing at first, but I promise it will be come clearer and clearer over time.
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