A PC (personal computer) card is like a special piece of paper that you can put into your computer to make it do different things. It's kind of like how you put different Lego pieces together to build a cool castle or spaceship
Some PC cards are for things like adding extra memory, so your computer can remember more things at once. Others are for connecting your computer to things like cameras or headphones.
When you put a PC card into your computer, it's like your computer is reading a special set of instructions on the card. The card tells your computer how to do something it normally wouldn't be able to do by itself.
So, in a way, a PC card is like a magic card that makes your computer more powerful and helps it do more cool things!