The correct term for managing and provisioning IT environments using descriptive, machine-readable files to automate infrastructure setup and maintenance processes is 'Infrastructure as code.' This practice enables rapid and consistent infrastructure deployment. It is distinct from 'Automated system deployment,' which may simply imply the use of automated tools to deploy systems but does not entail defining infrastructure in code. The term 'Software-defined networking' refers specifically to network management and not the broader scope of IT infrastructure. 'Infrastructure as a service' refers to providing virtualized computing resources over the internet, which does not capture the concept of provisioning through code.