avoir = to have

                                            j'ai                        nous avons

                                           tu as                       vous avez

                                           il/elle/on a              ils/elles ont

avoir is used to tell your age.

j'ai douze ans            I am twelve years old.

avoir can also be used with many expressions describing your feelings.

il a sommeil             He is sleepy

nous avons faim     We are hungry