DLL files are behind a large percentage of software errors and crashes yet few know what the abbreviation DLL means let alone what or why they are. DLL stands for “Dynamic Link Library” and a dll file is a set of miniature programs or files, usually used by multiple applications that reside in the system folder or the folder from which the application is executed.
Though not a rule, dll files are normally associated with simplifying low-level tasks for applications. For example, d3d8.dll file is Microsoft’s way of simplifying the extremely difficult task of rendering magnificent 3d graphics by providing the generic functions necessary to do so in a simple package.
Another purpose behind them is to save storage space. Certain functions, such as a print function call, are used by multiple programs and for each of these to natively implement the function would be a waste of valuable hard disk space. A dll file provides the function to all the applications that need it without them needing to have the code built-in, thus increasing their size.
On the software development side it makes developing programs much easier with ready-made functions provided by dll files.
In relatively simple words, a dll file is a group of non-independent programs that provide necessary assistance to larger ones.