Microsoft today announced a new home page experience in Office 365 for its current Exchange or SharePoint customers. This new home page will be the central place from which users can access all the services available to them. If you are a Office 365 ProPlus customer, you can also access the downloads to install the Office applications from this page. Below that, you will have links to all Office Online applications right from Outlook to OneDrive. If you prefer landing into some specific apps when you login via Office 365 portal, you can do that as well.
You may prefer to use a different start page. Instead of landing on the new home page, you might want to start in Outlook, OneDrive, SharePoint or Yammer. In order to accommodate a variety of start preferences, we’re also providing the ability for you to determine your own default landing page when you sign in to Office 365 via portal.office.com. You can set your start page preference with a few clicks. Click the gear icon in the top right of the navigation bar, and then click Office 365 settings. On the settings page, click Start page on the left hand side, select the page you want from the drop-down list, and then click Save.
Read more about it here.