DLL is a short for Dynamic Link Library, a library of executable functions or data that can be used by a Windows program. DLL can contain not only simple data, but also provides various functions and program accesses that functions only with the help of created either a static or dynamic link to the DLL.
A process is a piece of computer program, adding up one or more threads, that is being sequentially executed by a computer system that may run few more computer programs compatibly.
Every program is a files compound. When you launch the program you start an executable file that runs the entire program or just any other of its components.
An executable file, when it’s launched, loads a part of its code at the computer’s memory. That code is a process. Hence, the running program is represented by its fundamental process.
Computer parasites also have processes. Though, unlike ordinary software, their processes run without user knowledge. You can not terminate the parasite just closing application’s window. It’s not a solution. Therefore, you have to know how to kill malicious processes. » Read more: A Guideline of Killing Malicious Processes
Registry is a database used by the Windows operating system (Microsoft Windows 9x, Windows CE, Windows NT, Windows 2000, Windows Millennium, Windows XP, Windows Vista ) to store configuration information.
The registry contains information that Windows constantly uses in its operations, for example: profiles for every user, applications installed on the computer, types of files that can each configure, property sheet settings for folders and etc. The registry is common to several Windows operating systems, although there are few differences among them. » Read more: How to edit Windows Registry?