Wholesalers, brokers and real estate agents all serve as middlemen between buyers and sellers, connecting the two to help initiate a home sale. The defining differences between these roles turn on whether they require licensing, how they make their money and whether they involve becoming a principal in the transaction, meaning whether they ever own the house being sold in the deals they facilitate.
Real estate brokers and real estate agents have to be licensed (realtors are just real estate agents or brokers who are members of the National Association of Realtors, which is a trade association). They are not principals in the sales they earn money from, meaning that they never own the property. They make money by charging a fee, usually paid by the seller.
On the other hand, a wholesaler may decide to use methods that involve owning the property for a short time before selling it and doesn’t usually have any licensing. The buyer, not the seller, pays the wholesaler’s fee.