Short for back to back
1) Two DJ
s playing together. While one DJ is spinning a record, the other one is picking a new track. As they normally store their records behind them this usually makes the DJs face backwards on each other.
2) Business to business - there are two parties involved in financial or business transactions, traditionally sales of goods or services.
1) "The DJs at Intents Festival were amazing, especially Adaro b2b with Ran-D!"
2) "The local shop does business in b2b markets."