A lot of those counters are for internal diagnostic troubleshooting. They are not meant to be customer consumable. Engineering is the only one that would look at that data because of internal code structures and so forth.
The interface statistics should be fairly obvious, with xmit meaning transmit.
What are the queries on sysstat? That KB Pedro mentioned documents statit fairly well. Since sysstat is an older command it isn't as publically documented, but we want to ensure any questions about it are covered in what we do have. Please let us know your questions and we'll answer them up.