What is the use of Contacts?

What is the use of Contacts?

Hi,

Other than being able to import, list, categorise and create groups, what else can I do with contacts?

It seems logical that I should be able to select a contact and choose to send an email to them, chat with them, video with them, share something with them, call them with skype etc.

Alternatively when I am using Zoho Mail, when I chose Address Book, I was surprised that it was not the list of 'Contacts' that I had just populated. How do I choose a contact from my contacts list when I am sending an email from Zoho Mail?

Thanks

Luke