Use rasberry for other purposes

[EpicWings]

Hello raspberry world,
I am newcomer in this world and i would like to ask you a general question. From what i know raspberry have RAM which is a temporary memory but it doesn't have any storage. So here is my question:
If I download retropie on a card disk and use usb stick for roms ,can i simply take the stick and card disk off and use others usb sticks for other purposes(like raspbian and other projects). My main purpose on rasberry is to learn how to use retropie but i also want to have a second purpose where i can learn the others beautiful things that raspberry offers me. Can i have on a first stick retropie and on a second stick raspbian so i change them when i want or i need to uninstall them one by one to use them?
Thank you for your replies!!

[mitu]

@EpicWings Sure, you can switch the sd-cards. Note that RetroPie's image is just a Rasbian Lite system, it's not locked down and you have the whole OS at your disposal to tinker.
You can have SD card with RetroPie and one with Raspbian Desktop installed and you can switch between the cards - just make sure you shutdown safely the running OS before removing the cards.

[Efriim]

Hello,

Yes, as long as it is powered off the raspberry pi is ready to boot one 'image' or another on any drive.

The ability to boot from usb is possible and it takes some additional programming outlined here. If the usb mode is programmed the ability to boot from a SD card or a USB is granted. Additionally the ability to boot from SD card will be unchanged. Lastly the boot order while powering on will detect a installation on a SD card before a USB.

'Noobs' installation is an easy way to manage start up and it is possible to have multiple operating systems on one disk. Retropie is built on the raspbian distribution which is based on debian linux. Many of the things learned can be applied interchangeably.

Learn a lot, and you're welcome.