Folder encryption encrypt folder level while full disk encryption encrypt the entire drive or disk. Full disk encryption is not effect against hackers or viruses because they penetrated your computer, full disk encryption already decrypted your drive. The security door is widely openly. However folder encryption can provide protection that full disk encryption can not provide. Folder encryption can still protect data even though a hacker and a virus try to steal your data. However folder encryption could be powerless if the data that a hacker or a virus trying to steal was already decrypted at the time of theft attempt.