Microsoft’s Insider Hub is the tool that allows users to get news about upcoming Windows 10 builds and to send feedback on Windows 10 bugs or suggestions to Microsoft. It's currently only available to install on PCs running Windows 10 Insider builds, but it used to be also available on phones.
Let's go back in time for a minute: when Microsoft released the first Windows 10 Technical Preview versions for PCs in 2014, the Insider app was then pre-installed on all enrolled machines. The first Windows 10 phone build was only released in February 2015, at the time the Insider app wasn't preinstalled on enrolled mobile devices, it only appeared after a few builds had been released to Insiders.
In June 2015, Microsoft stopped including the Windows Insider app on phone builds, thus relegating the app a PC exclusive until now. Windows 10 Mobile Insiders have been questioning Microsoft for a long time regarding when the Insider Hub app will return to mobile devices, and today Gabe Aul finally answered this question:
@maaub It will be available in the next preview build from the Development Branch.
— Gabriel Aul (@GabeAul) February 10, 2016
The return of the Insider Hub to mobile previews is really good news due to its convenient feedback process. Right now it's not really convenient for Insiders to have to use an enrolled PC to access the Insider hub app for mobile. We will tell you more about the mobile Insider Hub as soon as Microsoft releases it in the next preview build.