A service charge assessed by an agent in return for arranging the purchase or sale of a security or real estate. The commission must be fair and reasonable, considering all the relevant factors of the transaction. Commissions vary widely from broker to broker. 

The brokerage with the lowest commissions is not necessarily the best one - you get what you pay for. Discount brokerages offer no advice, which can prove to be troublesome for many rookie investors. On the other hand, full-service brokerages offer a more personalized service, but commissions are much higher.