Whats a VLAN (Virtual LAN)

[DeeVeeDee]

My understanding of this is when you configure I.E a Cisco switch into Sections then in the end resulting into 3 different Switches in one ?
Which is not visable by one another.

Or the Other Way Round Multiple switches become one big switch.

Please explain it in simple terms ive tried Wiki but everyone wants to sound clever and they all use big words.

[Ryan_Cooper]

My understanding if I'm not mistaken it is more commonly the idea of having many devices on a network seem as if they all belong to the same Local area network irrespective of the geographical/physical location of the devices, similar to how a VPN works. Another instance is when you have a switch or many switches configured in such a way that different devices on the same network think they are on different networks, this is usually used when you want to split your Local area network into different parts say for different departments in a company or building