Freight brokers and Freight Forwarders do similar work so in a way they're similar to each other.
But freight forwarders specialize in arranging storage and shipping of merchandise for customers and sometimes take possession of that merchandise while freight brokers may do the same in arranging shipping and storage of the merchandise but freight brokers do not take possession of any merchandise from the customers.
The main difference between freight brokers and freight forwarders is that freight brokers do not take into their possession of merchandise.