XBoft Folder Lock 1.1 is on GOTD today. Generally this sort of encryption app, like those that hide folders, are lighter weight alternatives probably better suited for protecting stuff you don't want other users of the device to see, e.g. family members. I don't think there's anything wrong with that myself, as long as as the person using it is aware of the limitations. An encrypted zip or 7-zip file is likely more secure, but it's not really that convenient, e.g. for max security you should erase the unencrypted files when you're done with them. Microsoft's BitLocker encryption works, but it's sorely lacking when it comes to ease of use, particularly if you only want to encrypt a non-system drive or partition. That leaves VeraCrypt, the improved, open source successor to TrueCrypt.
veracrypt[.]fr/en/Home.html
[Note: I write drive/partition as a sort of reminder that every formatted drive has at least one, and possibly several partitions. Most everything you do pertains to the partition(s), not the actual physical drive. The drive letters you see in Windows Explorer for example are for the partitions. Selecting a drive in a backup app is more a shortcut for selecting all the partitions on that drive.]
Like TrueCrypt, what VeraCrypt does is that it either encrypts a real, physical drive/partition, or it creates a VHD [Virtual Hard Disk] that's encrypted. Anything stored on the encrypted partition, real or virtual, is encrypted when it's written, decrypted on-the-fly when it's accessed, e.g. opened or copied/moved. This happens automatically when the encrypted disk/partition is mounted, which is the part where you supply the password. Like all encryption, when you can access the unencrypted files, so can anyone else with access to your device -- if someone(s) has remote access because the system's been compromised [hacked, malware etc.], they may be able to see what you see for example.
A VeraCrypt VHD is much like any other VHD -- it's a single file that can be copied, moved etc. Note: backup apps sometimes don't work well with the file making up a VHD, and usually provide no benefit, e.g. reduced file size, compared to simply making a copy of the VHD's file. Many companies call their encrypted VHDs "Safes". Like the VHDs you can create in Windows 7-10, a VeraCrypt VHD can be a fixed size or dynamically expanding. It takes time to write the file used by a VHD -- the larger the file, the longer it takes to write it. With a fixed or static sized VHD, that time's spent when the VHD is created, and from then on the only delays are from the increased operational overhead of using a VHD, because you're relying on software vs. hardware to provide disk access. In contrast the file for a dynamic VHD is created at the smallest physical size possible, growing only as needed, but that growing process, increasing the physical size of the VHD's file, takes extra time. You either spend the time at the beginning, creating a fixed size VHD, or in increments whenever the dynamic VHD grows.
One feature of a VeraCrypt VHD is that the free space -- the part of the disk that doesn't [yet] contain any files [data] -- is filled with garbage data, unlike the free space on a regular physical drive/partition. You can create an undetectable VeraCrypt VHD inside the free space available in an *Outer* VeraCrypt VHD -- it's undetectable because there's no way to distinguish between the garbage data and that making up the encrypted *Inner* VHD. And it takes no extra work to mount that inner VHD -- when you mount the VHD you either use the password for the inner or outer VHD. Outside of some pretty sophisticated tech used by the likes of the CIA, I don't believe that there's any other way to actually hide files/folders in any sort of foolproof method. Common folder hiding apps use drivers to tell Windows Not to see a folder, so disabling that driver [e.g. Safe Mode] or using another OS [e.g. a bootable USB stick] that folder's accessible. You can stick whatever you want in the outer VeraCrypt VHD, so whomever sees a reason for the encrypted VHD to exist, and stick whatever you want, including a working copy of Windows, in the hidden one.
You can also use VeraCrypt portably, so you can have a USB stick with both VeraCrypt software & and encrypted VHD. It's easier however, though probably less secure, to use an app like Gilisoft's USB Stick Encryption, where the VHD is hidden, and the only dialog is a simple, small window asking for name and password. With VeraCrypt you have to start the app, select the VHD, and then enter the password. It's not hard by any means, but the Gilisoft app is easier. That said, the Gilisoft alternative is not fully portable -- it will add a driver to the copy of Windows you were running when you decrypt and open the VHD, so it might be easier for someone to tell forensically that you ran the Gilisoft app at some time in the past.