05_misc_repos = here are repositories from which it has built the client-side, and exe patched.04_useful_tools = here are different useful tools that you usually will need when will work with the emulator or databases.
03_openserver = here is Open Server (MySQL server where stored your game database and which required by the emulator).02_client_side = here is your client-side what need to copy-paste to your clean kRO client.01_emulator = here emulators (pre-compiled and pre-configured) for RENEWAL or classic PRERE mechanics.
We can find here a good guide on how to configure everything by yourself: This package good demonstration of how everything should be configured by yourself to make it work. Do not use this package anywhere in production. This is a newbie package that contains 1 click solution for launching Hercules emulator with a single click. This pack already pre-configured and compiled, you need not do anything here, just download, extract, run. TL DR: If you're a newbie, and want to launch a Hercules emulator and try it in 5 mins, just download everything here, extract, run OpenServer, Copy client files to kRO folder, run emulator, run client, login and play or do whatever you want to do.