What does gravity mean?

For example, what does it mean?

"grav: 0.43"

Code:

http://www.clickbank.com/help/affiliate-help/affiliate-basics/finding-products-to-promote/

LMGTFY

Code:

http://lmgtfy.com/?q=clickbank+gravity

It shows how many different affiliates have brought sales for that product.

Clickbank Gravity
Shows how many affiliates had made >=1 sales over the past 60days.

If you got one sale today, you've just add 1.0 gravity into the vendor's product.
Let say you can't get any further sale, you gravity will become 0.96 i.e you've just reduce 0.04 gravity from the vendor's product.
Multiply 0.96 everyday if you didn't get further sale, gravity reset whenever a you make a sales within 60days periods.

Hope it helps.