How can I categorize my client portfolio?

How can I categorize my client portfolio?

I am including a list of possible clients and I am brand new with Zoho.
What I can see so far is that all clients are saved under the same list and my question is how to keep a subdivision among them.
I would like to have my clients/ Possible clients list under Detailing, Distribution, Washing systems, and so on instead of all mixed together...

Thank you