I know this will probable sound like a dumb question but i'm new here. So what does sub-MOA mean?

"Sub-MINUTE OF ANGLE",,,

100yd -- less than 1"

200yd -- less than 2"

300yd -- less than 3"

and so forth.

Mil-dots and Minutes-of-angle, From a Technical Perspective

Quoted: I know this will probable sound like a dumb question but i'm new here. So what does sub-MOA mean?

It's not a dumb question. Generally speaking, as previous posters indicated, a 1 MOA shot grouping is going to be within a 1 inch area at 100 yards.  Because a "minute" is a subdivision of a "degree" (as on a compass) 1 minute is the deviation in measurement of angle of the bullet from it's aimpoint. When you speak of SUB-MOA that generally means consistently less than 1 inch groups. some will refer to 1/2 MOA and 1/4 MOA. The farther away you get, the larger the shot group, even with a flat trajectory bullet, because of the minute of the angle. A 1 MOA(within 1 inch) grouping a 100 yards could group three inches at 300 yards, for instance, but to defer with SBR7-11 a bit, this depends quite a bit on the balllistic characteristics and trajectory of the cartridge/projectile, wind conditions and a plethora of other factors. It is not necessarily linear as SBR7-11 suggested, although it can be. He was probably oversimplifying to illustrate the example.

Strictly speaking, MOA refers to the angle of deviation from the intended aimpoint, although it is commonly used to mean "within X inches", e.g. 1 MOA=within 1 inch@100yds, 1/2 MOA=within half an inch etc.

If you have a 1 MOA or less rifle, you have a very accurate weapon, if you can repeat it consistently. A gun vise will allow you to determine this without shooter skill being a factor.