A hub just connects computers. All incoming messages are sent to all connected computers.
A switch will use MAC addresses to optimize connections. Unlike a hub, it will send incoming packets to one other computer thus limiting the traffic in the network. All connections are treated the same.
A router will use IP addresses to optimize connections. It will send incoming packets to a single connected computer. Unlike a switch, it may provide additional services like NAT, DHCP, and DNS. Usually, there is a special WAN (wide area network) connection that represents an unmanaged connection or upstream. The WAN connection is used to connect to a modem, another router, or switch.
Some people describe the ability to allow traffic from one connected computer to another connected computer without repeating it to the WAN as a Switch. I am not sure that distinction is important anymore since it is ubiquitous.
Most routers will also operate in switch mode. Switches never operate as routers. You would never connect a switch directly to an ISP (internet service provider).
A LAN (local area network) can be created with at least one router and zero or more switches. There are optimization issues for how to choose the devices and topology.
A home LAN is usually created from a single router. I believe the internet simulator is set up to look like what a student would find at home.