Function execution order

Ok, a simple situation: say I have five fairly complicated functions on one frame. I define all my functions, what they do, etc. After all that, I call all five functions in a row like

functionOne();
functionTwo();
functionThree();
etc

so that they all run. Now my question is does the first one start running then the second one starts running whether the first is complete or not, OR does the first function run, complete, and then the second function run, complete, and then the third function run, complete, and so forth? Does it execute all the functions at about the same time or does it process one function at a time before moving on to the next?

Any help would be appreciated. Thanks.