It is to record your birth for the state/country you were born in. It is you first form of ID, and you will need it to prove your age when you start school. You will also need it to get a driver's license, and a marriage license.
A birth certificate is a vital record that documents the birth of a child. It has information such as when and where a birth occurred and who the parents are. These days birth certificate records are used as identification documents that are needed for school or sports registration, traveling (like if you need to get a passport), or for genealogical purposes. You can obtain a birth certificate record either by contacting the local government agency (where the birth occurred) that handles vital records, or there are trustworthy alternatives such as VitalChek https://www.vitalchek.com/birth-certificates that act as a link between those agencies and offer easy online ordering.