All too often people post using various abbreviations and acronyms. Unfortunately, all too often other people don't understand them!
Ideally, everyone would carefully use the full words in their posts, at least for the first mention. However, we live in a real world where people don't realise what they are doing.
Until everyone does that, this document might help:
For anyone reading this:
My Abbreviations and Acronyms document is permanently being enhanced. If you have not recently downloaded a copy, please feel free to download it again. There have been at least ten updates this year - so far.