Top of Book (Best
Bid/Offer) market data contains all top bid, bid size, top ask, ask size, last trade, trade volume, and timestamp data for exchange traded products.
Source (with edits):
https://www.cmegroup.com/confluence/display/EPICSANDBOX/Top+of+Book+-+BBO
Top of Book data forms part of the Order Book, other parts of the Order Book include
Depth of Market (or
Level 2 data)
Also abbreviated as ToB and BBO.
Also know as Level 1 data.
See also:
https://en.wikipedia.org/wiki/Financial_quote
https://en.wikipedia.org/wiki/Order_book_(trading)
