EXE file has Entry point, but in dll no Entry point.

EXE file is a excutable file which runs in a seperate 
process which is managed by OS,where as a DLL file is a 
dynamic link library which can be used in exe files and 
other dll files.
In .net frame work both are assemblies.

EXE is a Self Executable File where as dll is not self 
executable file,To run dll file we need a exe file

DLL:
1)it has versioning
2)it is not self executable
3)it runs in application process memory
4)it has no entry point
5)it is reusable

Exe:
1)it is self executable
2)it has no versioning
3)it runs in own memory
4)it have main function(Entry point)
5)it is self executable

Note:DLL is Superset of Exe

The full form of EXE is executable file,AND The full form 
of DLL is Data Link Library.

The full form of EXE is Executable file and DLL is Dynamic
Link Library.