Difference between layers with and without plus sign

Just a quick question (I think i’ve heard it explained before but can’t remember where).

I just noticed that some of my layers have a big black plus sign on them, while others don’t. What’s the diffrence between these two “layer types” and can you “convert” them to each other?

The big plus sign just means you can expand it. If it doesn’t have one it means you can’t expand it.

You can’t “convert”, it happens automatically depending on the needs of the layers.

OK Thanks :slight_smile: