There is a good description of .RESX files here: Resources in .Resx File Format[^] which explains the file format (XML) as well as touching on what it holds. Basically, it's a human-and-machine readable file which holds the images, icons, text (including - but not restricted to - localisation strings), sounds, and other resources that your app needs to have compiled into it that the compiler uses to build your final EXE or DLL assembly.
Bad command or file name. Bad, bad command! Sit! Stay! Staaaay...
