What is defined as "any component that needs to be managed in order to deliver...

CIs are simply any component that needs to be managed in order to deliver an IT service. A server, a virtual server, or even the configuration of an application could be considered a CI, for example

https://www.bmc.com/blogs/itil-asset-configuration-management/#:~:text=among%20your%20CIs-,Configuration%20items%20(CIs),considered%20a%20CI%2C%20for%20example .