BRRR Further Elaboration

[Bryant Amundson]

Can someone further elaborate on the BRRRR strategy please?

This is what I know: 

I pay X for down payment on a property. Then I rent it out, fix it up, etc... Then in Y amount of months I can refinance that property and pull my X down payment out to then use that X for a down payment on another property. 
Here's where I'm confused, in episode 169 of BP Podcast David Green talked about nearly paying off an entire mortgage then refinancing and pulling out all of that money. Maybe I heard him wrong, but maybe I just don't understand pulling money out of a mortgage or how the whole equity thing works. 

Disclaimer, I am new, I have no investments, but I am thinking the BRRRR strategy is going to be my go-to... That is once I completely understand it.

Pumped to read the wise words from the many minds that stumble upon this post.

Thanks in advance!

-Bryant