Final answer:
The term used to refer to all of the computer-based information systems used by organizations and their underlying technologies is IT infrastructure.
Step-by-step explanation:
The term used to refer to all of the computer-based information systems used by organizations and their underlying technologies is IT infrastructure.
IT infrastructure encompasses the hardware, software, networks, and data centers that support an organization's information systems. It includes servers, storage devices, operating systems, databases, and communication networks.
For example, in a company, the IT infrastructure would include the servers that store data, the network that connects computers, and the software applications used for various purposes like email, customer management, and accounting.