This question tests how serious
you are to working for the company.
Recruitment offices and interviewers are swamped with potential candidates, and don't want to spend their time on candidates who won't ultimately accept an employment offer.
Use this question to showcase the research you have done on the company and your overall interest in working with the company and the team.
Know what products and services the company provides, what type of organisation they are (small, global, not-for-profit) and approximately how many years they have been in business.
Figure out what awards they have won in their industry through lists like the Sunday Times Best Companies To Work For
Fortune 100 Best Companies to Work For
Go on Glassdoor
and determine the company culture, whilst identifying employee reviews that resonate with you.
If given the names of your interviewers, try to connect with them on LinkedIn
and see what their paths in the company have been like.