What is the passage mainly about? [originaltext] Greetings and introductions

Greetings and introductions are an essential aspect of U. S. culture, the importance of which can never be overemphasized.
    In social situations, a man is traditionally introduced to a woman. However, in the business world, introductions are based on a person’s rank or position in a company. Whoever is the highest-ranking person is introduced to everyone else in order of their position. If you introduce two people of equal rank to each other, [12D] introduce the one you know less well to the one you know better.
    There might be occasions wherein you will have to introduce yourself. For example, if you are meeting a new colleague or an associate, you might start off by extending your hand and saying "Hello! I am…". If you have been introduced earlier to someone, do not assume that the person would remember you and be prepared to reintroduce yourself should it be necessary.
    [13A] Americans shake their hands when first introduced to new people. Rarely do they shake hands while parting. As a part of greeting, sometimes, social kissing is acceptable between men and women and also between women who know each other very well.
    If you are with a group of English-speaking people and the conversation is going on in English, do not use your native or any foreign language for more than a few sentences, as it is not considered to be polite. Try to avoid using any filthy, sexually explicit stories or jokes. When you are in a theatre, it’s not polite to talk or whisper during the performance.