Candidate relationship management is defined as the process of attracting and engaging candidates, and nurturing authentic relationships with them over time. Candidate relationship management software used to do a single thing: help large companies source top talent ahead of a requisition.

CRM systems work to scale a recruiter's sourcing efforts by attracting passive candidates ahead of demand. ... In other words, an ATS is a workflow and compliance tool for managing applicants, while a CRM system is a pool of all passive and active candidates, as well as previous applicants already in your system

HR CRM is the combination of both CRM and ATM in the core operation. In other to have powerfull ATM you can develop more feature for HR CRM to meet your recruitment process.