I think that's how many millimeters thick it is. 

Mil layer is just short for millimeter - so a 12 mil laminate floor is a lot sturdier than an 8 mil because of it's thickness

Personally, we opt for luxury vinyl plank flooring with a 2 millimeter overall thickness and an 8 mil wearing surface in every property we renovate.This runs us about $3.00 per square foot once you include the shoe mold.

These shrink a tiny few millimeters per decade. 

Examining every square millimeter of the place with an electron microscope?  

While it was long believed to have a slip rate of around 14 Millimeters per year, Science Advances’ research argues that it's actually around 22 millimeters!

He claims it's 20 mils, but I'm wondering if he means 20 millimeters thick vs. the wear layer on the top?

But if you give humans a millimeter, they'll shove their foot in the door and pry it open and next thing you know you'll be babysitting while they're in Aruba after you lowered their rent because the husband got laid off!

@Brandon Stevenson I recommend (unless the moderators shut down this comment for answering your question with a recommendation) a 5 millimeter thick vinyl plank floor with the pad attached.

You can have 8 fully paid for duplexes and cash flow 14k a month with 2.4 millimeters n in assets.