A stroke is a relaxing movement of something against your body. A stroke gives you pleasure.
- Stroking your hair with a brush is relaxing and feels good.
- A lover can stroke your face, hair, leg, or back with his hand or fingers.
Different strokes for different folks means that different people are pleased by different things. Some people are pleased by hurting others, some by helping others. Some like pain; some like pleasure.
It basically just means that "everyone is different from each other."