Back in October 2014, we announced release of the Office 365 app launcher and My Apps—places where you can organize and personalize your list of first-party services accessible in Office 365.
This week, we’ve started deploying an Office 365 Store to make third-party solutions manageable in the same way, where external web applications can be launched with a single click—all within the Office 365 experience and with no admin configuration or additional sign in steps.
Read more at source: https://blogs.office.com/2015/06/25/office-365-users-gain-one-click-access-to-third-party-apps/