What are linked accounts

What are linked accounts

Hello, 

I'm new to Zoho - I'm testing it out with a view to bringing my email over to it - using my own domain with the 'Mail Free plan'.

As I understand it, I won't have access to IMAP on this plan, so can't use any other email clients other than the Zoho webmail or Zoho app.

Q1. Is it possible to comfigure these to pickup mail from other clients like Gmail? 
Q2. I looked at 'Linked Accounts', but I don't think that's what I need is it? What do linked accounts do? There are explainers in the knowledge base to set this up, but it doesn't explain what it does. 

Thanks in advance :-)