These are pattern files to be used with ImHex to inspect Morrowind's esm, esp, ess and bsa files. These are based on the similar patterns by Greatness7 for 010 Editor.
Start ImHex. You'll need to add the folder where you cloned/downloaded this repository to your include paths. To do so, once in ImHex, go to Extras > Settings > Folders. Once there add the folder to your list of included folders (this is a one-time process). This will allow ImHex to pick up the correct include paths used in these patterns.
Now you are ready to open some of the Morrowind's files. Go to File > Open File..., and open Tribunal.esm. Then you'll get the main view of the hex editor. Then, open the pattern for your file type: File > Import... > Pattern File. You'll get a Choose file window. Press Browse... and then open the correct pattern file from the folder you cloned/downloaded this repository.
Thanks to Greatness7 for his binary_templates on which these are based on.