EX: when you hit two buttons instead of one for a special move, and you flash yellow and it becomes faster or stronger, etc. Not all special moves have an EX option.
Reset: when your opponent is getting “knocked down,” if you hit him with most normal moves as he’s falling the combo counter will come up, and the character will flip and start to fall normally and be able to parry before he lands. There are a few moves that knock down, oro’s standing MP, remy’s jumping HP or crouching HP, too many to list, though. Yang has a couple reset options, if you hit them with the close MK, the palm strike, or HK (or EX) rolling kick, they’ll be knocked down but fly high enough to reset.
“SA” is short for “super art.” People use this terminology more often than typing a super’s entire name because people either can’t spell it properly or don’t want to take the time to write a long, obscure japanese phrase.
You should check gamefaqs.com for basics, or the Yang Everything thread for some cool stuff (start from the beginning), but I’ll outline a few things here.
The combo you’ll be using the most often is crouching MK into slashes (quarter circle forward (qcf) and any punch, repeat the entire motion three times for the combo). You can also connect into slashes with standing MP, but you’ll most likely want to use the crouching MK for it’s range and speed. Also consider his two chain combos: LK, MK, HK (stun, pushes back, good counter if you suspect someone will attempt to throw you or you want to ward off dashes), and MP, HP, back HP (knocks down, pushes far, fairly good damage).
You can keep away with standing HP, and occasionally with standing HK. MP is good if you want to advance slightly. You’ll find all of his crouching normals useful except perhaps HP. Crouching MP has very good priority and recovery, though.
If you want to know a cool reset that deals insane damage, get someone in the corner, and attempt a palm strike (half circle back (hcb) and punch). If it hits, they’ll fall pretty quickly, but there’s a small window in which you can hit HP and catch them before they land. The two hits deal about 40% stun on most characters and just under 1/4 life. Note that you can fake the palm by pressing two punch buttons (yes, that means there is no EX version).