Okay, so imagine your immune system like a superhero team in your body that helps fight off bad guys (like germs and viruses) and keeps you healthy. As you get older, this superhero team starts to get a little tired and not work as well. This can make it harder for them to fight off the bad guys and keep you healthy.
This is called immunosenescence, which is just a fancy way of saying that your immune system gets weaker as you age. It's kind of like a superhero team that has been working for a really long time and just needs a break.
But don't worry! There are things you can do to help keep your superhero team strong and healthy even as you get older. Eating healthy foods, exercising, and getting enough sleep are all ways to help keep your immune system strong. And if you do get sick, your superhero team will still be there fighting to help you get better!