F10 ("step over") does not descend any further into the call stack. It moves to the next line of the current function.

F11 ("step into") drills down into the function being called.

void function1()
{
    function2();
    function3();
}

If you hit a breakpoint on function2(), F10 will advance to the line function3(). F11 will advance to the first line inside function2.