Relationship between Zoho Projects, Zoho Business, Portals, etc.

Relationship between Zoho Projects, Zoho Business, Portals, etc.

I am still not certain about the relationships between different groups of information in Zoho.

What is the integration between Zoho Projects and Zoho Business?

What exactly does a Portal represent?   I was confused because we can have more than one portal in a login ID.   And are we one "User" (in terms of Business or Projects) in a single login ID?

In a word, how are all the features of Zoho organized?   I'm still having a lot of difficulty understanding this.  It's a large collection of great features that seem to be thrown together randomly.