[Oh no, don't do that, you will unlock Luca's inner nerd.

Or outer nerd because he doesn't really hide it, but. Here it is.]

To condense it down a bit, it is the application of one's own willpower to the world around themselves. Some tools are needed to do this- drawn circles, for one, not unlike the alchemy circles and magic circles that have been shown around here- but the majority of it has to do with how strong your willpower is and how creatively you can think.