Relax, you don't have to read or understand this section in order to use Folder Guard. We have provided this information only in case you are really curious. You can safely skip this section and go to the next one.
As you probably know, most Windows programs don't work with files and folders directly; they rely on the support provided by the Windows operating system to work with files and folders. (It makes each program able to work with wide range of the storage devices, letting Windows take care of the details). For example, if you use Windows Notepad to open a text document, the Notepad program first prepares a special request for the contents of the disk and sends this request to Windows. Having received the request, Windows searches its internal data structures and the contents of the disks, and returns the results back to Notepad, which in turn shows the files and folders to you in the Open File window. After you have selected the file and pressed OK, Notepad prepares another request for opening the file you have selected, and sends it to Windows, as well. Windows reads the appropriate bytes of data from the disk and returns them back to Notepad, that shows them to you in its window. In reality, the procedure is much more complex: even a simple operation like the one described above may take hundreds of different requests sent back and forth between the program and Windows, before you can see the results on the screen. All such requests and actions are performed by the programs transparently to you, and you don't even have to know what is going on under the Windows hood, unless you really want to.
Folder Guard works by intercepting the system requests that Windows programs and Windows itself exchange between each other. Folder Guard analyses the requests and the data they contain, and uses the attributes of the files and folders that you have set up with Folder Guard to allow or deny such requests. For example, if you designated a file to be read-only, and some program sends a request to read information from this file, Folder Guard allows such request to go through without intervention, and passes the results from Windows back to the program. If, however, a program sends a request to write some data into such file, Folder Guard intercepts it, and returns it back to the program without passing it to Windows. This prevents the file from being overridden (as per the read-only attribute), and makes the program display an error message such as "Access denied" or similar.
That's how Folder Guard works.