A useful distinction
A frame is a presented image; elapsed time measures how long an interval lasted. The relationship can vary with the environment. An action defined only by a number of frames may behave differently when presentation timing changes.
Put it into practice
For a prototype, write whether a movement depends on a turn, an input event or elapsed time. Test the assumption in the chosen tool using its maintained documentation. Avoid copying a timing technique from an unrelated example without understanding the conditions it expects.