To Grid or Not to Grid that is the problem! (AND your little furniture too) :)

[Gamerprinter]

And if the grid is hinted to in the drawing of the rooms instead of being explicit lines, for instance a chequerboard pattern of tiles, then what?

Aside: What is "VTT", I'm asuming a file type meaning something along the lines of virtual terrain tools or similar, and follow up, what programs use them?

VTT are virtual tabletop applications, software that lets you either create a map using built-in paint tools, or import maps created in other software that can have grids placed on them, fog of war - which is the ability to hide areas that cannot be seen from PCs exist on the map (areas hidden by obstructions like walls, trees, hole, etc), objects, PCs and NPCs are on separate layers allowing you to play RPGs online with a shared map and use of Skype or messaging software so that GMs can speak with players, or players can speak between each other. Its a way to run a tabletop game with GM and players using internet connected computers to share the visual and play experience in separate locations - even playing with people across the globe. MapTools, Fantasy Grounds, Battlegrounds, Roll20 are all examples of VTT applications.