What is the difference between a skin care shop and a dermatology clinic?

My skin isn't what it used to be, so I'm thinking of getting some treatment, but I don't know where to start.

Since it is simply dry and dull, I am confused whether I should go to a skin care shop or if it would be better to have my skin examined at a dermatologist first.

I'm worried that if I try various treatments for no reason, they might not suit my skin, so I'm currently looking into it.

I used to think that just buying one good cosmetic product was enough, but as I get older, it seems I need to set a specific direction for my skincare.

I would like to hear the experiences of those who started skincare for the first time and what they began with.