EXE and DLL are both types of assemblies. The difference being EXE is a self executable file and DLL is basically loaded into any program and program can use the supported methods and properties of the DLL.Exe has a entry point that is understood by the windows process so that the process can launch the application. DLL is just a library file which do not have entry point.To be more specific, if you create windows application you have a Program.CS file which has a main method. This is the entry point that tells the operating system to launch the application and OS can read the entry point in the header of the PE file. DLL is a class library project where you do not have any methods like Main or files like Program.cs.