How do we categorise hand-holding? Have you ever wondered why such an act can trigger all sorts of emotions within you? What message do you relay when you hold another person’s hand?
Wikipedia lists the reasons and purposes when two or more people engage in the act of hand-holding and I’d like to cite some of them:

Rituals
Expression of friendship or love
Enjoyment of physical contact
Emotional support
Physical guidance
Dancing
Arm wrestling

With that said, I’d like to focus on it being an act of expression of friendship and love.