Office 365 is an online platform of various office and collaboration applications. The home page allows the subscribers to navigate to various apps like SharePoint Online, Word Online, Excel Online, Project Online etc provided you have the subscription of those applications.
Sometime a situation might arise that you might need to change the default URL of the tile. For example, the default URL of the tile Sites (SharePoint Online) leads to a page other than the SharePoint instance home page. This page shows you the number of sites you are following. Whereas the homepage of your SharePoint Online instance will be different. If you want your users to be able to click on the SharePoint tile and go to SharePoint Online home page then Microsoft says it is not possible to change the URL in the default tile. However, they suggest that you can create a custom tile with the URL you need and hide the default tile. The custom titles will appear via app launcher > view all my apps.
To add custom tile to the app launcher you would need access as a global admin of overall O365 tenant.