ASO and SEO is totally different things the basic concept is same to make WEb and APP more visible.

ASO and its need
 

ASO is the abbreviation for the term app store optimization.

this ASO means optimizing your app in the app store in such a way so people can see it more.We should try to optimize the app as per parameters given by that app store.

ASO is helpful to rank the particular app in top of the app store

trough the ASO we try to reach that goal.
ASO is the Part of SEO.