I've experienced it many times with my students and also with myself. Let me illustrate with example:
When I'm teaching, I say something like this:
Gastrointenstinal Track has following sections
- Buccal Cavity
To help them remember I repeat above thing multiple times. But still they don't remember much of the list.
Alternatively instead of just saying those things (even though that's all I need my students to remember), I spoke about each of the above item for few minutes. i.e. I gave more details of about each of those things. Result is that, now my students do not remember most of the details about each of those items, but they could remember the list. Which is exactly I want.
Whats happening here? Whats the science behind it? Is there more to what I'm describing?