In LeadSimple, contacts are a data card of a person and their contact info.
Leads or deals are the actual relationship that a contact is either in (current client or tenant) or in the process of becoming (owner leads, tenant prospects, buyers, sellers, etc). A contact might be in multiple deal relationships (such as a current tenant who is also a prospective buyer). Likewise, a deal might have multiple contacts connected to it.
A process might have multiple contact roles involved in the process.
When adding contacts to LeadSimple, be sure to add them as both contacts and deals, rather than simply contacts, to accurately track the relationship you have with them.