.dll is for reusable component and .exe is executable files

DLL has no main method Exe has main

It’s called an assembly.Whenever we create any program in .NET it generates an assembly.Assemblies will either have an extension of .DLL or .EXE.Good to know: For example if we compile a windows or console application, we generate a file with an .EXE extension, where as when we compile a web or Class library project we get a file with .DLL extension.