Bare bones basic definition of a switch is simply a multiport bridge allowing many end user devices to connect via Ethernet cable to the network. An interesting analogy is like a power strip that you can plug multiple devices into for power.
The same holds true for the switch, but it instead provides a network connection on the Local Area Network (LAN).
Interestingly enough, a switch can also provide power to some devices, such as VOIP phones, wireless access points, and even cameras, but that may be for another post.
Thanks for your blog, nice to read. Do not stop.