On most transactions, there is usually a listing agent and a selling agent. The selling agent is sometimes referred to in media as the buyer's agent, because he works on the buyer's behalf and it easier than explaining each time that the "selling agent" is not the listing agent and is actually the buyer's agent.

However...

There are some agents that market themselves as "buyer's agents," "exclusive buyer's agents," buyer's representatives," and so on. Mostly it is just marketing. At the same time, part of it is because they want to accentuate the reasons a buyer should not go directly to the listing agent when they purchase real estate. This has to do with agency.

See, if a buyer goes directly to the listing agent, they are dealing with an agent that has conflicting responsibilities. Their job is to get a good price for the seller and they may not zealously represent the interests of the buyer. Those who market themselves as "Buyer's Agents" indicate they are only working for the buyer in a real estate transaction.

The commission is still paid by the seller, no matter what they say in their marketing (with extremely rare exceptions). They either get paid directly by the seller or set up the transaction so that the seller provides a "credit" to the buyer for how much the real estate commission is -- then the buyer pays the commission.