Well kiddo, a royal bastard is a person who is born to a king or queen, but their parents were not married. This can happen when a king or queen has a child with someone they are not supposed to, like a mistress or a commoner.
Being a royal bastard can be a bit complicated. Since they were not born into a married royal family, they may not have the same rights or privileges as their half-siblings who were born to a royal couple. This means they may not be in the line of succession to the throne and may not have access to the same resources or titles.
However, sometimes kings or queens acknowledge their royal bastard children and give them special titles and positions. And sometimes, the royal bastard children can grow up to do great things, even if they don't have all the same advantages as their siblings.
So, being a royal bastard is kind of like being part of a royal family, but not really. It can be a bit confusing, but it's just another way that families can be different from each other.