Simply put it's a GUI to launch Sensible World of Soccer game in an emulated environment.
What makes it special is that it contains almost all variations of the game and data related to the game that has been released in almost 30 years, officially and unofficially. The GUI lets you to choose any combinations of that data, from graphics and sound sets of different game versions and platforms to team/player data from different years.
There are tons of data disks to choose real-world event setups from 1930 to 2022, which are result of work by the SWOS community. Tournament setups can be viewed as well as other documentation. Gameplay tactics can be changed from original releases and there's an extenisive Tactic Viewer to analyse the new updated tactics/formations. The pack also includes special versions of the game from magazine cover disk releases to versions from other platforms (SNES, GameBoy, Game Gear, Master System).
Some binary patching takes place to let you to define players for loaded DIY competition and to make results random, which they weren't in the original version.
There's also some other functionality that doesn't affect to the game itself, but is for convenience if you want to arrange multiplayer competitions at events or hack SWOS files yourself. The pack also contains intro animation, music remixes, cracktros to launch with the game, etc.
There are similar "total packs" for PC, but Cool_amigaN has made a huge work by compiling all the data and knowledge, and created/processed Amiga compatible files over and over again, to make this pack for our platform. And I've been helping to fulfill his wildest dreams in code-wise :P
So, you could say it's the ultimate collection of data to play for every SWOS maniac with everything at your fingertips. And it improves the original game series in many aspects.