I'm a little confused as to Campaigns VS Marketing Hub. 

I currently use Campaigns and want to ramp into Marketing Hub. 

When I look at lists in Marketing Hub, I see my Campaigns lists and the interface starts to look at lot like Campaigns. 

1. Is Marketing Hub an "overlay" of Campaigns? Meaning does it leverage what I've built in Campaigns?

2. Should I be using Campaigns for my CRM Client emails and Marketing Hub for my Leads? (I'm seeing my Clients in Marketing Hub too but the term "lead" is very dominant in Marketing Hub). 

Thanks,

Scott