This is a pretty small computer part. It's not too expensive but not so many people have them actually. It's not rare but not everyone has them. And what it does is it allow you to other people when you are chatting online.
You might be too young to know what this is because people hardly use these at all anymore but they were used for storing memory. But they have basically gone out of style because they can't store nearly as much memory as some newer memory storage devices.
If your computer didn't have this, it wouldn't work. Your computer definitely needs to have this. I don't know how it works, it looks really complicated but I'm glad it works.
This part is also absolutely necessary for your computer to work but it's nearly nearly as complicated as the last question. You plug it in to the wall and it provides the electricity to power your computer.
Now the last two question I said were necessary for your computer to function but without this one there would never be computers at all. There would be no one to invent them and there would be no one to use them. This is the reason why we have computers.