blowby
 

I've never heard of it. What is it, what causes it, and how do you fix it..Thanks.

basically it is when your compression goes past the piston rings and into your oil pan. to fix that you need to clean the carbon off the piston rings and if that doesn't work you need to chage the rings and sometimes pistons

does it burn oil?

blowby is just combustion gases getting into the crankcase. it's why you have a PCV valve.