Basically this is a VST to emulate loop launching (session view) in Ableton Live in Reaper.
From their homepage:
Playtime is a VST instrument for the Digital Audio Workstation REAPER and works in REAPER only. It is designed to make loop-based music production in REAPER easier and much more fun. In particular, it offers a Session View loosely inspired by the one in Ableton Live. That means it enables you to play loops in a very intuitive way - just by triggering them using your MIDI controller or the graphical user interface.
Basically this is a VST to emulate loop launching (session view) in Ableton Live in Reaper.
From their homepage: