Ubuntu Unity is a new flavor of Ubuntu that uses the Unity Desktop Environment.
The Ubuntu Unity project is leaded by Rudra B. Saraswat who wants to give a new life to the desktop environment Unity7 on Ubuntu. Currently at the stage of remix, Ubuntu Unity aims to become an official Ubuntu flavor in the future. This is why this distribution doesn't contain any external PPAs
The display manager ligthdm has been replaced by GDM3. Other changes include a default Yaru + Papirus theming and the Unity Tweak Tool which comes preinstalled with the distribution.
It includes i386-arm that sets up an emulated Debian i386 (9) environment. This would help you to run 32-bit programs on your Raspberry Pi from the terminal.
More info available in in this blog post.