Many employers are very supportive of internal promotions and hiring employees who are ambitious enough to have goals including long term career growth. It sounds like the employer you're talking to fits in that category.
That said, employers are trying to balance that with filling an immediate need in a specific role. If they're hiring you as a Basketweaver's Apprentice, it's because they need a Basketweaver's Apprentice, not because you want to some day be a Basket Supply Chain Manager.
So - if your employer is talking about their strategies for promoting from within, consider that a long term benefit and not an immediate, risk free plan. In other words, don't take the Apprentice job only because you want to some day be a Supply Chain Manager. However, since they have initiated the conversation about being promoted to other positions, it's completely acceptable (and probably a good idea) to discuss which other positions you may want to pursue in the future. By doing so, you're showing that you will fit their culture well, and you're ambitious enough to want to grow. Just make sure you're doing it within the context of also being committed to the actual position you've applied for, and showing interest in, and skills required for, doing that specific role.
In other words, don't let the promise of future promotion get you too carried away.