A conquistador is a Spanish explorer, like the ones that explored America. They were important since the Spanish would not have spread their empire without someone to lead the way.
An immunity is something that means you cannot get harmed by since you have already had it or have medication to make yourself invincible to that disease. It's like after having chicken pox, you can't get again.
I hope that this is the answer that you were looking for and it has helped you.
