The console in NWN allows you to input console commands / debug commands. The Debug panel allows some shortcuts and more advanced options as well. The debug mode is only available in singleplayer with Debug Mode on or if you are a DM.
Many of the console commands do not have a nwscript equivalent so may be useful for DMs or when part of a persistent world.
Using The Console
There are two main ways of using the console.
Press the tilde key - ` - in the top left of the keyboard to open the console. This appears with a yellow > character. Then you can type and tab complete commands:
Chat using the in-game chat function, with two hashes, allows chat commands, eg: ## ModAge 10
These can also be added to the quickbar if you right click and empty spot and select Custom Text Macro:
Then enter in the given box the same as the chat command:
Using the Debug Panel
To open or close the debug panel press CTRL + SHIFT + F12. Note the debug panel contents can change regularly as things are moved around (to/from options, to/from console commands).
Alternatively search for it in the options to toggle it on and off: