In "Triangle 5ABB11", we see that spells do not need to define every bit of the actions or physical presence that occurs and this is the danger - that there are unintended consequences because what happens in a spell is usually far more complicated than the actual words used. The creation of Olaf the Troll and Thor's hammer were not in the spell, but they appeared as fully functional items.
I would compare it to using a computer - each letter of a response that I type is decoded from the keyboard, assigned a place in memory, steps the cursor along, checks for buffer overflows and a lot of other operations I may not be aware of. But it all happens anyway whether I am aware of it or not. A spell is akin to using a high-level language or app on a computer - the user is relieved of the necessity to do all the work but in return, loses some awareness of what is happening.
