NppExec is a plugin for Notepad++ which allows you to run some commands/programs directly from Notepad++ and provides an output window (NppExec's Console).
NppExec can be used for running other programs from Notepad++, passing text from Notepad++ to some external tool, compiling source files (using external compiler) etc.
When the NppExec plugin is installed, you can see its icon "Show NppExec Console" on Notepad++'es toolbar, and you can find NppExec's submenu under Plugins menu of Notepad++.
You can always find the latest version of NppExec at https://sourceforge.net/projects/npp-plugins/ - it is there among other Notepad++'es plugins.
The latest sources of NppExec can be found at https://github.com/d0vgan/nppexec/ .