Hi @Oran,
The values BID (BID_1) etc are the latest BID values. The BEST_BID1, etc are best BID values during the trading day. Note: BID, BID_1 are rippled meaning the BID_1 is copied when a new BID comes in. The BEST_BID1, BEST_BID2 are not rippled but represent the best BIDs ranked.
For content questions related to meaning of FIDs for example, the best resource is to ask your questions via my.refinitiv.com.