name typically used to differentiate people from the same family, clan, or other social group who have a common last name
A given name (also known as a first name, forename) is the part of a personal name that identifies a person and differentiates that person from the other members of a group (typically a family or clan) who have a common surname. The term given name refers to a name bestowed at or close to the time of birth, usually by the parents of the newborn. The term Christian name is the first name that which is given at baptism historically in Christian custom.
In informal situations, given names are often used in a familiar and friendly manner. In more formal situations, a person's surname is more commonly used—unless a distinction needs to be made between people with the same surname. The idioms 'on a first-name basis' and 'being on first-name terms' refer to the familiarity inherent in addressing someone by their given name.By contrast, a surname (also known as a family name, last name, or gentile name), is normally inherited and shared with other members of one's immediate family. Regnal names and religious or monastic names are special given names bestowed upon someone receiving a crown or entering a religious order; such a person then typically becomes known chiefly by that name.
Read more or edit on Wikipedia