Anthropology is based on the idea that human behavior can be best observed and explained by comparing it to other human behavior. As explained by Boston University's anthropology department, 'anthropology begins with a simple yet powerful idea: any detail of our behavior can be understood better when it is seen against the backdrop of the full range of human behavior.' Using what is known as the comparative method, anthropologists make attempts to explain similarities and differences among people holistically, in the context of humanity as a whole.
To simplify this, how about we give an example of the comparative method? Suppose a young girl in let's say a very fundamental Islamic Saudi Arabian family is given her very favorite toy for her birthday. I mean, it's the toy she's been waiting for her entire life! When she opens it, she will feel joy. However, because of the accepted rules of her culture, she will most likely not jump up and down and squeal in delight. Instead, she may give a polite, small nod and a smile. Yes, she will be joyful, but to the Western mind, she will look subdued.
Now, what an anthropologist would do is to take this Middle Eastern scene and compare it to its American counterpart. They'd seek to understand why an American girl would squeal and dance around the room when seeing her present, but the Middle Eastern girl would not. Both girls experienced happiness, but they expressed it quite differently. To an anthropologist using the comparative method, this sort of stuff is golden as they seek to understand the universal human emotion of joy as it plays out in different cultures. In other words, the comparative method helps an anthropologist understand how a person's environment affects how they act.