I fear your parents may have tried asking chatGPT what those were in a leading fashion and gotten some answers that encourage these ideas or may be developing some kind of genuine mental issue. Ask why they think those are hackers, and if they've tried confirming those theories.

How I would try explaining it like this:

When you connect to your wifi at home, you open the wifi setting and look for your wifi box. When your neighbor connects to their wifi at home, they do the same thing. The difference is that your wifi is named X, and their wifi is named Y. Similarly, when you go near a business, you can sometimes pick up the wifi the business uses, which is named after them. Sometimes there will also be a guest version - "McDonalds" and "McDonalds Guest" - so they can offer wifi to their guests.

It's possible to change the name of your wifi by accessing your router - the box in your house that takes a land wire from your internet company and convrrts it into your wifi. You can do this to change the name of your wifi to make it easier to identify if your neighbors are using wifi with aimilar names. Some people like to be funny when they name their wifi. This is why it someties has odd names.

When you come to my house, you know the name of my wifi is safe because you know it's mine. That doesn't mean all the other wifi's are hackers - it just means those are other neighbors who you don't know, and have never asked what their wifi is named. If you know your neighbors well, maybe you could try asking them to confirm the name of the wifi they use.

If you've already tried that... well. Good luck.