The AST is the representation of a program that gets turned into what the computer can understand

Whether interpreted or compiled this is almost always the case. Following is the way that loon ,an interpreted language, traverses the AST (in normal speech)

There is a function called evaluate.
Who a single object it will take.
If it not be list it returns just this.
But if it is then more work we make.
take the list turn it into a stack , vector often will do.
pop the top, look, and here we eval anew!
If it is function then who would have guessed
we apply it to the evalled next.
Otherwise, quite a suprise return the top popped!
(if none then be just vexxed)

Of course this description skips over a bit, such as checking symbols against the dictionary and stuff but I could not figure out how to fit those into the poem.