Answer:
Courtesy is a social skill that facilitates social interaction. In essence, it comes down to showing respect for someone through the person's attitude and etiquette. The opposite is called rudeness. The forms of courtesy are strongly time-bound, and also differ from country to country. In Japan, for example, people bow to each other, while in the west they shake hands when they meet. Another form of courtesy, largely lost in the course of the twentieth century, is holding a door open for a lady, which a well-bred gentleman ought to do. With the emancipation of women, this was less appreciated.
Thus, courtesy is an attitude towards other people that does not have a cost, that is, it does not imply an effort for the person, but that has a notorious benefit for those who handle themselves through said manners, inasmuch as it makes their relationships social are much more positive.
