You learned about broadcasts earlier, and how a router does not pass along broadcasts. In a typical network, everything on the same side of the router is all part of the same broadcast domain. A switch that you have implemented VLANs on has multiple broadcast domains, similar to a router. Managing a project or working with a specialized application can be simplified by the use of a VLAN that brings all of the required nodes together. Since a principle element of a VLAN is the fact that it does not pass broadcast traffic to nodes that are not part of the VLAN, it automatically reduces broadcasts.
Access lists provide the network administrator with a way to control who sees what network traffic.
An access list is a table the network administrator creates that lists what addresses have access to that network. While you can have more than one VLAN on a switch, they cannot communicate directly with one another on that switch. If they could, it would defeat the purpose of having a VLAN, which is to isolate a part of the network. Communication between VLANs requires the use of a router . VLANs can span across multiple switches and you can have more than one VLAN on each switch.