B share is the leveraged gain side of graded funds. Graded funds generally divide their shares into A and B. B pays interest to A and invests with A's funds. However, after paying interest, the overall investment profit and loss is borne by B's share, which is highly variable and the wind direction of A's share is relatively small.
For the safety of A's principal, graded funds generally have discount clauses. When B's net profit drops to a certain extent, in order not to affect A's principal, B's shares will be merged and part of A's shares will be distributed to investors as dividends to restore investment leverage.