hello, Happy New Year !!
Ovi.com is the application that is within Nokia "cloud" so to say. your phone has the ability to sincronize contacs online, this is similar to Google contacts or Microsoft Myphone apps. You need to be registered with Ovi for this. And you have to in order to download from market..
Ovi suite is the "old" PcSuite that Nokia had... is the software that syncs photo, contacts, tasks, web favorites you have in your phone with your computer. Usually connected with the MS Outlook application, works pretty fine.
Main problem i found with on-line sync, to all three, OVI, MyPhone, or G-Contacts is that sometimes screws up the last name with forename of one contact or more... other than that no major problems.
having contacts in sync with an online service is better in the event that you loose the phone or format it by accident , or delete all contacts in outlook.... but i'm not sure about privacy..