A listing agreement is an exclusive agreement between the seller and broker to market their house. An exclusive buyer representation agreement is an exclusive agreement between the buyer and their broker to find them a home.
Exclusive means there is only client and one broker. There are non-exclusive agreements where there can be more than one broker for a buyer or seller. Real estate agents prefer to have exclusive contracts so they have a better chance of earning a commission rather than competing with other agents.
For example, if a broker has a non-exclusive contract with a seller, the first one to bring in an acceptable offer gets a commission. They could be competing with a dozen or more other brokers so how hard are they going to work on their behalf? I only work on exclusive contracts because I want to be able to devote 100% of my attention to my clients. This benefits both them and me.