These files, called 'mod', allow the user to modify the original version of the game.
If this is what you want, you will be pleased to discover that the Minecraft community is huge and made up of a large number of programmers, who take on the creation of 'supplementary files' with the aim of enriching the game and breaking the monotony that inevitably affects Minecraft players. Do you have a Minecraft server and after several game sessions you no longer find the right challenge and motivation to continue playing it? Would you like always new updates introducing new features to make your explorations less boring?