you get to see your laptop on a (most likely) bigger area or you can set it up to be extra real estate(one document on your laptop and one on your extra monitor)
WIFI can connect PC and laptop.
usb connector
no you can not do this. you can only use an external monitor on the laptop.
by line connection
A crossover cable.
You connect a PS2 to a TV not a computer monitor.
network hub
You can connect a laptop to a PC through a docking station, but it will not improve performance. However, you can connect your laptop or PC to a server, storing most data files on the server and this will increase performance slightly by freeing up hard drive space on the laptop, or PC.
Connect a router lead from your internet box (if you have one) to your laptop.
Check what kind of connections the monitor uses, then compare to the motherboard of your PC, or laptop.
connect your ps4 to your pc or monitor
The best way to connect your laptop to Internet when is already being used by your PC is to add a router. Depending on the router you select, you can then connect your laptop to the router or you can connect wirelessly. This will allow you to have more than one computer on the Internet at the same time.