: .7z is a highly compressed archive format. You will need a program like 7-Zip or WinRAR to extract it.
: v1.0 suggests this is the first full release or a specific milestone build. FutanariOfTheApocalypse-v1.0-pc.7z
: pc indicates it is the Windows/Linux version (likely a Ren'Py or Unity build). FutanariOfTheApocalypse-v1.0-pc.7z