Zoho docs. How does it work?

Zoho docs. How does it work?

I'd like to know better Zoho world. I'm a member of an italian society and we are interested in a file manager to file our documents. Actually what we need is Zoho docs, I suppose. Unfortunately, I haven't understood how it works. Does every section have a pricing plan? If I want to use zoho docs but also the contact manager, have I to buy both versions?....sorry I'm a bit confused. Hoping someone can help me.
Anyway, basically we need to store docs!

thank you