I work as an IT manager when I'm not a Google researcher, and this is
the kind of question that is routine on any job description for anyone
considering working in IT.
ICT stands for Information and Communications Technology (and is
commonly used as a European industrial classification). So the ICT
infrastructure is an overall name used to describe all the computer
and communications hardware and software used to manage clerical,
administrative, and management tasks in organizations.
To have "a sound knowledge of ICT infrastructure", you need to be able
to show that you understand
- the basics of what computers are used for,
- how they are used in business,
- what kinds of hardware are used and why,
- what kinds of networks are used and why,
- how to deploy software across networks (and why you would need to),
- how PCs work,
- what a "backup" is and why you'd use one,
- how inter and intranets work and how they are managed,
- how computer security works and how to impose it,
.....the list goes on to cover all the operational and support matters
you need to think about to purchase, build, install, run and manage
computer systems in organisations.
In effect, you need to understand how computers integrate into a
company's business, and how they are managed.
Here's a glossary of basic computing terms - you'd need to know what
most of these mean if you were to show a "sound knowledge" of IT
( http://www.labourtel.org.uk/glossary.html )
Most businesses have strategies in place for managing ICT
infrastructure. You can see what is involved in a fairly typical
example from Australia here:
State of Victoria Education and Training
As you'll appreciate, this is a very big field, and getting bigger all
the time. A "sound knowledge" takes time and experience. Good luck.
search terms used
"ICT infrastructure" basics
"ICT infrastructure" glossary