The Konkrete mod is a mod library that is used to run some other mods for minecraft. By itself, the mod does not add anything to the game and does not change it, it is necessary to install it only if it is required by some other mod, for example FancyMenu.
How to install the mod:
Install Forge or Fabric
Install all additional mods if specified.
Download mod and copy to .minecraft / mods
In the launcher, run the forge or factory version of the game.