Unlike console ROMs (like NES or SNES), MAME ROMs are not single files. A single arcade game can consist of dozens of smaller files: program code chips, sound chips, graphics data, and sometimes a parent ROM with regional variants (clones). When you download a pack, it typically contains hundreds or thousands of these zipped game folders.
If games aren't loading, you are likely missing the required BIOS file in your roms folder. mame roms pack high quality full zip android
Clone games rely on a "parent" game zip file to run. If you delete the parent, the clone stops working. This saves storage space but makes file management difficult. Unlike console ROMs (like NES or SNES), MAME