The specific naming convention "2559osub" suggests a categorized backup or a "beatmap pack."
: Use a tool like 7-Zip or WinRAR. Right-click the file and select "Extract here."
is an archived file format typically used for distributing specialized digital content, most commonly associated with beatmaps for the rhythm game osu! . The ".7z" extension indicates it is a highly compressed archive created with the 7-Zip utility, designed to package multiple files into a single, smaller download. What is a .7z File?
: These are the individual levels or songs in the game.