What are those symbols for the different spells?

I think it is just part of the game to follow the letters that is all...I don't think they are the real wand motions. Take for example the body-binding curse (Petrificus Totalus) which the 'wand motion' looks like a hook in the game... I don't recall seeing Draco doing the wand motion for it in HBP when using it against Harry.