What is the difference between oracle HCM and oracle HRMS?

Oracle HRMS is a specific module, among others in a suite of modules called Oracle e-Business Suite.

In a nutshell, Oracle e-Business Suite is an on premise business applications installed at the client site when the licenses are purchased either directly from Oracle or through one of its partners. Oracle HRMS is a module which belong to the oracle e-BS suite HCM.

Coming to Oracle HCM, it can be identified under two different suites of applications:

1. e-Business Suite HCM, which includes mostly the following modules. Each of these modules require a separate license.
1. Oracle HRMS,
2. Self-service HR,
3. Payroll,
4. Time and Labor,
5. Performance Management,
6. Learning Management,
7. iRecruitment,
8. Incentive Management,
2. Fusion HCM & Taleo, which includes mostly the following modules. Each of these modules require a subscription paid directly to Oracle (because most clients choose the Cloud based version). If a client chooses the on-premise option which is far more expensive, the same model applies as in e-BS (referred in point 1).
1. Global HR,
2. Payroll,
3. Absence Management,
4. Benefits,
5. Goal Management,
6. Performance Management,
7. Compensation,
8. Sales compensation,
9. Work life solutions, (my wellness, my reputation etc,)

Oracle has reinforced the HCM Cloud SaaS (Software-As-A-Service) recently by investing heavily in Fusion HCM and Taleo which now comes under the new umbrella of Oracle HCM.

Does it make more sense now? HRMS is a the core HR application of the old suite. HCM is the umbrella under which you find all the modules listed above.