When you first open up your Falcon site you are provided with various folders by default. None of these are just ordinary folders and you shouldn't rename and repurpose them. Instead start new folders by following the instructions (Creating a folder or directory).
If you don't want the default items at present, the best idea is to unpublish them (known as retracting them), so when you do need them you can publish them again (see Un-publishing default folders for how to do this). If you delete them instead and you later change your mind, you will have to ask falcon-support to create replacement ones.