How do I set up my Playstation 1 emulator files? [closed]

I recently got a Raspberry Pi 3 and I installed Retropie on it using my Linux system. I found out that it can emulate Playstation 1 games so I downloaded all three Crash Bandicoot games. When I extracted the .rar files I noticed that they didn't extract to .iso files. It made a folder for every one of them. The first two games have a .bin.ecm file and a .cue file and the third game has a .bin file and a .cue file. I haven't really seen anything like this with emulation and I am wondering how I would manage these files. Do I have to convert anything? Why are the files different? Also, do I put all the individual files into the rom directory or do I put each folder into the directory?

Note: I thought that it might be worth mentioning that for anyone who isn't familiar with Retropie the way that you add games to the system is use a fat32 USB drive and put a folder called retropie in it. You plug it into the Raspberry Pi and the Pi creates directories for all the different rom types. You can then put the USB stick back into the PC and put the extracted roms into the matching directories on the USB drive. When you plug it into the Ras Pi again it will copy any new roms from the USB drive to the right rom directories in the system.

Solution 1:

.ecm is a file extension often used in emulation to save a bit of space. You need a tool to convert it back to a usable format. Something like ECM tools