It's Mint's built-in version of redshift, it reduces blue light at night by tinting your screen orange to be easier on the eyes. It is installed by default on all cinnamon versions of Mint. It is not included with Xfce (not sure about MATE).

If you want something similar on Xfce, you'd have to install Redshift and manually configure it with either a schedule or a location for it to work automatically, as it has been abandoned and the automatic location finder is broken.