Dreamweaver Templates: What are optional and repeating?

[stylemaker]

Hello and thanks in advance for help with a newbie question about Dreamweaver Templates. I've read that there are three kinds of templates: editable, optional and repeating. Questions:
1) Are there three kinds of templates, or three parts to one template?
2) What is an optional template?
3) What is a repeating template?

thanks again! ... RW :)