"Half-caste" is a word that people used to use a long time ago to describe someone who has parents from different places, like one parent is from one country and the other parent is from another country.
The word is not used anymore because it can be hurtful and make people feel bad about themselves. Instead, we say "mixed race" or "multicultural" which means that someone has a family background from more than one place.
It is important to remember that everyone is unique and special no matter what their family background is. It is not polite to focus on someone's skin color or where they are from, but instead to get to know them as a person and learn about their interests and experiences.