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:
Several of these options are good for checking advanced textures such as in the Standard material inputs and will demonstrate the nature of the different ways the engine loads textures, eg: Material Metallic can show the shiny metal bits of things:
While the normals view shows the normal bumpmap textures: