Sortir is used when talking about getting out of a specific location, like a house. It's almost always used as sortir + de: "Je suis sorti de chez moi." (I left my house.) "Elle sort du bois." (She comes out of the woods.) Partir is often used when you have a physical destination in mind. "Je suis parti en France." (I left for France.) "Ils sont partis à l'étranger." (They went abroad.) But not always: "Il est parti chercher des cigarettes." (He went to look for cigarettes.) "Elle est partie." (She left = she's no longer here.) Additionally, sortir can be used in other ways that don't correspond to partir. It can mean: to take something out: "J'ai sorti les billets de ma poche." (I took the tickets out of my pocket.) In this case the auxiliary verb for the past is avoir rather than être. to go out with someone: "Je sors avec elle." (I go out with her.)

repartir = to leave again

We use sortir when the subject leaves a place, sortir means to go out, to exit: sortir d'une chambre, sortir d'une maison, sortir d'une place. Partir means to leave: je pars en France demain.

Sortir means "To go out" Partir means "To leave"