I had this on my OnePlus 6T and 7T. From what I understand, it will lock all your phone data in such a way that the only way to view the data will be through the phone only.
Normally you will not even notice that your data is encrypted if you turn it on, but if your phone screen is broken or not working, you cannot copy the data to other device as it will work only if the phone is unlocked.
You cannot decrypt it by yourself. For example, if your data is encrypted and your phone is stolen, the thief cannot take out your phone storage and copy data. The only way to decrypt data is to unlock the phone and then copy data to a pc or pen drive via otg. If the phone is locked then data will not appear on other devices. If your screen is damaged and you cannot access the lock screen, then the data cannot be recovered. I don't know if that is the case with samsung but it is how it works on OnePlus
It will encrypt ( change all your data's source code to a special , secret code to prevent unauthorized access) all your data including all the apps , logged in accounts , settings , media files etc.. to a special format,
Just like whatsapp messages are encrypted in between , only you can read what you write,
Just like if you say hi , it may convert it to bdi3794 etc...
