What connecting device do you use for a small LAN for two or more connected networks?

For a small LAN network, a switch is best. To connect two or more LAN networks, a router is required.

(2) From Jean Andrews CompTIA A+ sixth edition (page #852):

You can use a crossover cable to connect to computers without a switch or hub making it the simplest network of all. For two or more you will need a switch, hub, or router.