Alternate data streams (ADS) can be attached to files, directories or drives and are hidden from users who use Windows Explorer or similar file managers. You need special tools (like this one) to find, create, or remove (specific) ADS.
To access ADS without an application like AdsManager you have to know its name. Let’s say you have a file named myfile.txt. To display the content of a stream called mystream for example, you can write more < myfile.txt:mystream on the console. Notepad wants to have a .txt extension like myfile.txt:mystream.txt. The colon separates filenames from the name of alternate data streams.
Many applications cannot access ADS because they think colons are invalid characters in filenames. For that reason applications based on .NET Framework are not capable of using alternate data streams as well.
The DLL shipped with AdsManager makes it possible for .NET applications to access ADS anyway. Internally it uses native Windows API functions (which can deal with ADS) and provides an interface for .NET developers.