[markus_zhang]

Most of the retail brokrages (except maybe a few big ones) play a strategy of A/B book. Most customers are in book A which is essentially a casino (bet against the maker), and if someone is too good they just send him to book B to play against the market.

[nlitened]

The naming is vice versa for A- and B-book. B-book is playing against the maker. A-book is playing against the market (which is in fact "playing against a bigger maker down the line")

[markus_zhang]

Thanks! didn't know that