Repeat Step

Hi all, I’m still learning here and I know a lot of you have come from DMXZone with Dreamweaver (I haven’t).

Can someone explain the Repeat Step to me please? Is it like a while loop (while expression is true)?

Also, can someone provide some good, solid use-cases for this action?
My first guess was that if I wanted to mail every user in the database I’d query the database and then use a Repeat Step which would do the actual mail sending. If so, what is the expression set to? I may be completely wrong but hoping to learn.

Many thanks!