DLL stands for Dynamic Link Library which is a collection of small programs used by executable program (EXE) when running. They are generally (but not always) found in your Windows System directory.

DLL files usually end with one of the following extensions: .dll, .exe, .drv, or .fon.

Why are DLL files useful?

DLL help executables to communicate with the devices, such as printers, or contain source code to do particular functions. Even if the main program is loaded in RAM (random access memory), the DLL file is not, so that the space is saved.

DLL files that support specific device operations are known as device drivers.

For example typing something in a word document and printing that document, only for the second process the printer DLL file is called and now it is loaded into RAM.

Deleting a DLL file it is not such a good idea, because your DLL file might be used by more than one program. If you uninstall a program, and decide to delete the DLL file, this file might be used by another program. So when a program is being launched you will receive an error message that the file .dll is missing. You can recover your lost DLL file or you can search it on the internet because there are many sites that provide you support in getting the DLL file needed.