An arrival is an entrance or an appearance — the act of showing up somewhere. Your arrival at your grandparents' house will no doubt be marked by great enthusiasm and many hugs.
The process of arriving, or first getting to your destination, is arrival. Your sister's arrival at the airport might be delayed by bad weather, and your new kitten's arrival will be an exciting event for your whole family. Another kind of arrival is a person who's just arrived: "I easily picked her out from all the bus station arrivals."