ATK
 

im wondering if anyone can explain the stat ATK which is in my character screen. or maybe post a link to a breakdown of stats?

Without looking for the math behind it it's basically skills + str.

Some buffs can get +atk directly (used since str caps) I believe. On live ATK determined how high your max hit was hence it was very valuable to melee, especially rogues. I'm not sure if it functions quite the same on p99.

It determines how often you hit for max, not the max itself. Absolutely critical for rogues who have the biggest damage rangeyness. Offense, Str, and damage bonus are all that impact the max hit value.