We have just added a second laptop to our home network. A network error come up on the new laptop when closing down internet explorer saying 'IP address conflict. Another computer on this network is using the same IP address' or something like that.
But both of the laptops are able to connect to the internet and at the same time too.
I heard that two computers should never have the same IP address as results can be unpredictable. What does that mean?

Do I need to fix this? And if so how?