The clauses section
The clauses section is where you put all the facts and rules that make up your program. Clauses for a given predicate must be placed together in the clauses section; a sequence of clauses defining a predicate is called a procedure.
To satisfy a goal, Visual Prolog will start at the top of the clauses section and proceeds down through clauses, looking at each fact and rule and places internal pointers next to each clause that matches the current subgoal. If that clause doesn't lead to a solution, it looks for another match (backtracking).