Do you know what a custom is? A custom is something we do the same way over and over. Shaking hands is a custom in many places. It is a way of saying, "Hello."
Not everyone in every country greets others with a handshake. Their customs are different. It is interesting to learn about the customs of other countries.
In China men and women conducting business may shake hands. They may also nod or give a slight bow.
Russian people usually shake hands with people they have just met. Relatives and good friends are greeted with a big hug and a kiss on the cheek.