Both leads and jobs are technically projects. Every project has a status, and that status will either be under the Leads category or the Jobs category.
Defining which projects are leads and which projects are jobs is actually up to you! You can follow these guidelines:
A lead is a project that is a potential booking. Leads are often new inquiries or projects where you've sent a proposal but don't have a signed deposit or paid invoice yet.
A job is a for sure booking, however you define that! For many businesses, a job has a signed contract and at least a deposit paid on an invoice.
The idea is that new projects will start off with a lead status and eventually move over to a job status once they are booked. You can create custom project statuses under the categories of leads and jobs to more closely track the milestones in your process.