Forum Discussion
Storyline 360 Slides versus layers
A couple of things to remember,
The learner can't tell the difference between a new slide and a new layer, so the difference is mainly for the developer's convienence. Part of that decision is that they are distinct, and both have pros and cons. Read the posts linked in Joe's post, and see the discussion at https://community.articulate.com/discussions/articulate-storyline/philosophical-question-more-slides-or-more-layers. Especially valuable is the discussion referenced by Michael's post.
The other thing to remember is that both slides and layers are free. They don't cost you any noticable amount in terms of size, performance, or resources (until you get into the thousands.) But putting too much material on one of them can have a huge cost in the learning procss, A new slide is your friend, clutter is not.