The ascendant is the vehicle, the Sun is the driver. Who is driving that motorcycle- a 1st grade teacher? Who is steering that skateboard- a CEO? In the first case, the person may have an Aries ascendant with Virgo Sun, in the second, Gemini ascendant with Capricorn Sun. The vehicle and the person driving it may not have a lot in common, but they still come together. What you see might not be what you get. That dump truck may belong to a beauty queen.
If you have the Sun and ascendant in the same sign, then your vehicle might be more like walking- like taking yourself out for a walk. You walk your Sun around, and there is a thin veil between your ascendant and Sun, but it’s still there. You still need to remove your shoes and take off your coat to be completely yourself. There is almost no place you can walk in nothing but your bare feet. You need protection. You need an outer protective shield of some kind. The ascendant is that shield.
Your ascendant is the way that you get around, but it’s not you. It helps you navigate terrain and offers a method to interact with the environment. Your Sun is always the one in the driver’s seat while the ascendant comes equipped with the GPS.