for the last year I have heard about concave, abec, spec, 10 ball, center trac, terrapin, etc. but what is the difference in abec and spec? or 10-ball /spec…what is the difference in each bearing?
Mainly how they play but usually stock bearings are already pretty good. All the bearings just play differently such as the konkave it’s supposed to keep the string centered though i heard that i could be a bit snaggy also a bit loud, 10 ball is really smooth and very quiet… Its all opinion though i tried a 10 ball for my speeder 2 didnt like it. the other 3 bearings i havent tried (abec,spec,terrapin) I heard though the terrapin is nice. my personal fav is the center trac or the speed 
ABEC ratings are generally meaningless in the yoyo world. They apply primarily to tolerances and have little, if any bearing on quality.
To find out more, you can read the description on the YYE store. Some of them are self-explanatory. For example, Konkave bearings are concave in shape, allowing the strings to be centered during play, decreasing responsiveness.