How to stop Google Photos from backing up screenshots and other folders

If you are an Android user, then you must be aware of Google Photos and its feature that allows users to back up their entire gallery to cloud and free up space on the smartphone. Also, the app offers unlimited cloud storage if a user chooses to upload them in high quality.
However, even if you have unlimited storage on offer, you might not want to upload all the photos such as screenshots, random WhatsApp images or something which you have downloaded from the browser for a specific purpose and is not as important to keep a backup.
So, how are you supposed to ensure that only the required folders are being synced by Google Photos? Here is how to do it.