Best way to store data in online apps

i’m developing an online shop application using ionic v3 framework. i’m wondering if its better to store data on the phone or not? one solution is to keep data in a local database on the mobile phone , fill the tables when opening the app and drop them on exit. another way is to cache the loaded data and show them if the user came back to same page again. or maybe i shouldn’t store any data at all?
does anyone know how online shops like amazon app do this?