Purpose of "Topics" checkboxes in Conditional Build Tags dialog box?

When applying conditional build tags to Table of Contents topics, what is the purpose of the "Topics" checkboxes in the Conditional Build Tags dialog box?

Specifically, I would like to know:

1. What functionality does selecting/deselecting the "Topics" checkbox allow/disallow?
2. If the "TOC" checkbox is selected, should the "Topics" checkbox also be selected?
3. Is there any scenario in which the "Topics" checkbox would be selected, but the "TOC" checkbox would not?

I am using RoboHelp 2017.