VeraCrypt has different features or services to offer like system encryption. System encryption gives the highest level of security and privacy for all files, including the temporary ones that Windows and applications create on the system (with or without your knowledge or approval), inactive files, etc., are always encrypted permanently (even when the power supply is interrupted suddenly). This involves validation before restarting which means that if the user wants to gain access and use the encrypted system, read and write files saved on the system drive, etc., must enter the correct password every time before Windows launches.
Pre-boot validation is being handled by the VerCrypt Boot Loader, which stays in the first track of the boot drive and on the VeraCrypt Rescue Disk. Apart from this feature, VeraCrypt has so many features to choose from like Plausible Deniability, Pipelining, Parallelization and so much more.
Even if there is no information saved on an encrypted volume, it can still be readable without the need of using an exact, required password, or encryption keys. The whole system file is being encrypted (i.e., names of the file, names of the folder, the contents in every file, free storage or space, etc.)
The files that were saved can be duplicated from the mounted VeraCrypt volume in the same manner as they are duplicated to or from any typical disc. One of the examples would be the simple drag-and-drop functions. These files will be automatically being decrypted in the storage memory while they are being copied or read from an encrypted volume.
In the same case, files that were being duplicated or reproduced are being encrypted automatically on the file even before they were written on disc or the memory of the device. It is to be noted that this does not necessarily mean that the entire file that is about to be encrypted or decrypted must be saved in the memory before it can be encrypted or decrypted. There are no additional memory requisites for VeraCrypt.
It is to be emphasized that VeraCrypt would never save any data that were encrypted to a disc, instead, it only saves them in the meantime in RAM or storage. Even so the volume of the disk is being mounted, the data that was stored is still encrypted. If you relaunch or turn off your computer, the volume will be disabled and the files saved in it will not be accessible and encrypted. If the power supply suddenly being disturbed without the proper shut down on the system, the files saved in the volume will not be accessible and encrypted. On the contrary, in order to regain access, you have to do the mounting of the volume and fill in the exact, required password.