What is a VLAN and how does it work?
You seldom see a network of any size these days that does not have multiple, multiple connections coming into it from external networks (or the internet), and servers and wireless networks and any number of devices all of them interconnected together on that network and/or through it or to it.
Scarily enough, it’s not unheard of to HAVE all of these connections and devices on a SINGLE broadcast domain on your network, but this type of setup is very highly not recommended!
If you DO put all devices on the same broadcast domain, you’re asking for trouble – You could have traffic issues, collisions that never stop and most importantly you’d be putting your network at severe risk of security issues for multiple reasons (that we get more into detail with on the “New to Networking” Course).