Minecraft Realms is a service that existed on PC for quite a little while now. It's free and it lets you host servers easily to play and share worlds with your friends.
Sadly, it was still missing on mobile and made hosting quite complicated. The neat feature is that it continues to run, even when you're not there just like a dedicated server would do.
Once live, you'll be able to play with people owning the iOS, Android, Windows Phone and Windows 10 version.