Program dynamic link libraries (DLLs) can provide information about the functionality of a program. Here is a list and description of the most common Windows DLLs:
Kernel32.dll
Core functionality of access and modification of system memory, files and the hardware.
Advapi32.dll
Windows Service Manager and Registry access.
User32.dll
User interface components such as user controlled components, i.e. buttons and scroll bars.
Gdi32.dll
Graphics functionality.
Ntdll.dll
Windows kernel interface.
WSock32.dll and Ws2__32.dll
Network connectivity and related network functionality.
Wininet.dll
Application layer functions in networking, such as HTTP and FTP.