Definition
Infrastructure is the combined foundation of hardware, software and services that supports applications and business operations — compute, storage, networking, facilities and the operational practices around them. In speech and in technical writing it is often shortened to infra.
How it works
Infrastructure work means keeping servers, storage and the network available in a predictable way: procurement and racking, configuration management, monitoring and alerting, capacity planning. After the cloud arrived, part of this work moved into consoles and code.
Usage
“Working on infrastructure” can mean building your own facilities and networks, or defining resources on cloud computing platforms with tools like Terraform; in AI companies, infrastructure often refers specifically to standing up and maintaining GPU clusters and training platforms.
Related and confusable terms
Infrastructure is the umbrella term for the underlying resources and systems; an IDC is its physical-facility part; a neocloud is a class of provider that packages GPU infrastructure and rents it out.