Create a Lead Record

Leads are created from contact records (Create a Lead Record from a Contact) and are a way to track potential business before you have a scope of work (to start a project) and before you want to start involving other users in your company in the process. Anyone can create a lead record as long as you have access to the contact record. 

Lead records also track your marketing efforts using Marketing Campaigns. 

Even if you are just going to create a project directly, you should create a lead if the customer (or potential customer) came to you by way of a marketing effort. This will allow your managers to evaluate whether a marketing campaign was effective or not and whether it is worth doing again. 

See here for additional details.