Comparative advantage is the ability of an entire group or a specific individual to carry out an economic cavity better and more efficiently than other activities. So basically doctors have a comparative advantage in the medical field whereas engineers have a comparative advantage in buildings and technology.
Similarly, teachers have a comparative advantage in teaching children and so on. It is the specific niche of a person or his place in the economic world. What he gives to the world tanks to his capabilities and excellence in that particular matter. This is what gives that person a comparative advantage over others.
It is the ability of an individual or group to carry out a particular economic activity (such as making a specific product) more efficiently than another activity.