What Does Core Switch Mean?
A core switch is a high-capacity switch generally positioned within the backbone or physical core of a network. Core switches serve as the gateway to a wide area network (WAN) or the Internet - they provide the final aggregation point for the network and allow multiple aggregation modules to work together.
A core switch is also known as a tandem switch or a backbone switch.
Techopedia Explains Core Switch
In a public WAN, a core switch interconnects edge switches that are positioned on the edges of related networks. In a local area network (LAN), this switch interconnects work group switches, which are relatively low-capacity switches that are usually positioned in geographic clusters.
As the name implies, a core switch is central to the network and needs to have significant capacity to handle the load sent to it. There isn't a precise definition as to how powerful this is, but clearly it is much bigger than an average desktop switch.