What is core switch?
A core switch is a high capacity switch that is generally located in the backbone or physical core of a network. Core switches serve as gateways for a wide area network (WAN) or the Internet - they provide the final aggregation point for the network and enable multiple aggregation modules to work together.
A core switch is also known as a tandem switch or a backbone switch.
In a public WAN, a core switch connects edge switches that are positioned on the edges of related networks. In a local area network (LAN), this switch connects workgroup switches, which are relatively small capacity switches typically located in geographical clusters.
As the name suggests, a core switch is central to the network and must have significant capacity to handle the load sent to it. There's no precise definition of how powerful this is, but clearly it's a lot bigger than your average desktop switch.