It would never need to note a port for the internet.
-> But this is the right device since your modem has to have a router in it because of what you wrote.
Think of this as an port expander for your LAN. One of the 8 ports will go to your modem+router and the others are for your PCs.
I need more ethernet ports, and I found this switch:
I have two questions about it.
Firstly, I do not see any one port on it that is labeled for connecting to the internet source. Does this mean that I can use any of its ethernet ports to connect to my modem?
Also, my modem has multiple ethernet ports, some of which are being occupied by computers. I have some folders on those computers shared over the network. If I connect a computer to the switch, would that computer be able to access those shared folders? Would it also work in the other direction, if the computer connected to the switch had some shared folders?