Why do some English names have more than two parts? (The parts are separated by dots)

English names are generally in two parts, the first name comes first and the last name comes last; In some cases, there will be a middle name. For example, some women like to keep their maiden name after marriage, which is their maiden name. She will add this to her husband's last name, and it will become a middle name. Others will accept a religious name after being baptized, which can also be used as a middle name. If this person is a woman, the married name may be four parts, first name+Christian name+maiden name+husband name. In addition, the United States is an immigrant country, and the names of immigrants and their descendants may have their own national characteristics. For example, people from Islamic countries or Arab countries often have several names, but in order to conform to American habits, they usually use their first names and surnames, and only write their full names on legal occasions or very formal occasions.