A DLL (dynamic link library) is a small program that is used for a specific
purpose by the main program that calls it. Windows programs like Word and Excel
call and use many DLL files.
Unlike most programs, that link and compile all the program elements they need before they begin executing, DLLs are only loaded and used as they are needed. This feature saves RAM space, which is a valuable resource. A DLL file usually has a filetype of '.dll'.
For example, when Microsoft Word is editing a document, the printer DLL file is not loaded into RAM. If the user decides to print the document, only then does Word load the printer DLL file.
Don't ever erase a DLL file unless you are positive it isn't needed by your PC. Erasing an important DLL file can make your PC inoperative until the file is replaced!
If you don't have a DLL you need, your operating system should display which one(s) it can't find, In that case you may be able to find and download them File.