Most people (in IT) understand the concept of vLANs and Private vLANs. So this is a simplistic explanation of vLANs to none technical people who might have waken up with the urge to learn about the mysterious concept of vLANs!
vLANs basically allow us to subdivide a physical network into separate logical networks. As per diagram below, you can see a physical network that has been subdivided into 4 logical (virtual) networks.
To help explain it better, imagine a hotel building (below image). It is a large building that has separate floors. Each floor represents a separate vLAN within the bigger container, the building! As each floor has a number, so does a vLAN. vLANs usually have an IP subnet.
Now lets take this further. Each floor has different guests. These hotel guests are asking for some privacy as they are getting tired of sleeping in one large room (this is not a hostel). So we build separate rooms on each floor for privacy and this leads me to the concept of Private vLANs (PVLANs). PVLANs are logical containers within a vLAN. PVLANs provide ability to restrict communication between machines on the same vLAN.
Now for a guest to go visit a guest on another floor, he/she needs to take the elevator. Similarly, machines located in different vLANs and need to communicate, they must use a layer 3 router (elevator) to pass their traffic through.
I hope this explained the concept of vLANs and PVLANS and I hope to add another simplistic post to explain PVLANs in greater details.
Thank you for reading.