Selling

• BIN- buy it now- means no bidding, just a straight sales price
• FAQ- Frequently asked questions- always check here before asking a question
• FB- feedback
• FVF- final valuation fee- what the seller is charged when they list and sell item

Quality of item

• NIB- new in box
• VINT- vintage
• NOS- new old stock
• DOA- dead on arrival
• VHTF- very hard to find
• NWT- new with tag
• NWOT- new without tag

There are many more abbreviations used that are category specific, but this is a great short list to get you started