An internet exchange point (IXP) is a physical network access point through which primary network providers connect their networks and exchange traffic.
IXPs provide a common place for ISPs to exchange their Internet traffic between autonomous network systems.
A Primary role of an Internet Exchange Point is to keep local Internet traffic within a confined area, reduce the costs, and improve the quality of Internet services. By having direct access to the infrastructure and to networks you want to peer with it reduces latency by reducing the length of the path that traffic needs to travel. In the end, an IX increases the resilience of the Internet by providing many more redundant routes for traffic, allowing congested routes to be avoided.
In order for peering to work efficiently, Internet Exchanges offer a neutral local network where any carrier, ISP or network operator can connect and exchange traffic. The IX uses switching equipment to build the local network, by placing equipment in existing carrier-neutral data centers - sometimes in more than one location for redundancy purposes and uses dark fibre to interconnect those locations.
Euro-IX, an association of Internet Exchange Points, made a video explaining IXPs: "Internet Revealed":