There are lots of words that mean to move slowly. The point of dawdle is that one is moving too slowly, is falling behind, or is not properly focused on making progress.
One way to remember the meaning of dawdle is that it rhymes with "waddle," as in, "a duck waddles." Imagine what would happen if you waddled instead of walked. It would take a lot more time, and your companion might say, "Don't dawdle!" Dawdle implies not only taking extra time but actually wasting it. A leisurely walk in the woods is one thing, but if you have to get to the theater on time, don't dawdle along the way: you'll miss the curtain!