I looked around the forum and did a search and couldn't find an answer to this:

I see many 2 and 3 letter abbreviations used in discussions here. I know some are airports (ORD, etc.), some are airlines (UA, etc.). I can look those up and find out what they mean.

But there are many other abbreviations used, and often I can't fully understand the discussion because I don't know what they mean. Some appear to be ticket classes. Some may refer to upgrades. Some probably refer to something else.

Is there a list of these abbreviations with their meanings? Here or at another website?