What is Leads?
Leads are contacts and companies you've not yet qualified.
A Lead is most of the time someone you've never been in contact with. The goal with a Lead is to get the first contact and qualify it to be an Account.
Leads is also a place for working with a lot of potential contacts and companies at the same time. If you want to make a lot of cold calls in a short period of time, Leads is the perfect place for this.
Why should I create a Lead instead of an Account directly?
Because you don't want your CRM to be cluttered with companies and contacts that are not qualified. Separating Leads and Accounts like this makes prioritizing easier for those who work with both new and existing customers.
Accounts are everyone we've had contact with and that we want to keep contact with. Leads are those who we don't know just yet.
Leads is an Add On available for Cirrus 2 users.