How does the red hair gene work?

One day I was thinking about what my future kids would look like ( if I have any in the future) and then I thought about if any of them would have red hair. My grandpa, aunt, and a few cousins have red hair, so I looked it up on google and got multiple answers for the red hair gene. Some said that both parents have to have red hair somewhere in there family, and then i got answers that say it skipped generations, but i don't know which one is right or are both right? Could someone explain how that works?