Cross-connections are hardware (fibre, switches, routers) that connect separate units of the facilities within a data centre. They are usually maintained by a single data centre or across multiple data centres, and can be used for many purposes.
Trading companies may use hundreds of cross-connections between servers to ensure trading takes place as quickly as possible.
Cloud providers use cross-connections to connect networks and Internet services providers (ISPs) within the same building and often for a single company.
Some companies use cross-connections to make sure their business is connected to global networks so they can take advantage of redundancy and pricing.