New to InDesign... can't figure out how to get type to the next line

I know there is probably a simple answer to this that I'm missing... but when I create a type box, begin to type and then need to start a new paragraph or hit return for whatever reason, my type box ends up with the text overflow "+" I cannot make lists and don't understand what I'm overlooking. I've been using Pagemaker and I'm new to InDesign. Please help!