Warm Calling is the process of reaching out a prospect with whom a sales rep has already had previous contact.
Previous contact can mean, an outbound campaign in the form of a cold call or email as well as having established contact during an event or even through a referral.
Further engagement in the form of warm calling represents building upon an existing interest providing a better opportunity for closing the deal due to the fact that the prospect being more open and the sales reps having gotten past a gatekeeper that can directly influence the sales process.