VeraCrypt is a great application to establish and maintain an on-the-fly-encrypted volume. On-the-fly encryption means that data is automatically encrypted right before it is saved and decrypted right after it is loaded, without any user intervention. This is a very secure method of data encryption as any data that is stored on an encrypted volume cannot be read (decrypted) without using the correct password/keyfile(s) or correct encryption keys. The entire file system is encrypted (e.g. file names, folder names, contents of every file, free space, meta data, etc) to give you as much security as possible.