What does BTA,non-BTA or smthing mean

Beat the average.

If you beat the average price on bundles, you (most of the time) get more games.

Beat (or below im not sure) The Average . means how much did they pay for the bundle. this will change what games are there ofc, less money less games usually ;)

BTA = Beat the Average. The bundle sellers usually have 2 types of bundles

The pay what you want ( Minimum 1$ For Steam/Desura Keys ) bundle containing a few cheaper games and the beat the average pack ( where the price changes influenced by the buyers - If people pay more, the beat the average price is lower and viceversa ) contains the pay what you want bundle + a few more expensive/better ones.

Ok,i got it now,thanks for clearing that up for me.