CCMA is a Certified Clinical Medical Assistant. This certification allows you to work in a doctor's office, health clinics, surgical facilities and hospitals as a Medical Assistant. Job responsibilities include (but are not limited to) checking patients in, taking vital signs, administering injections, dispensing medications, blood draws, performing and reporting point of care testing, EKGs, assisting with procedures, health records, patient education and anything else that the provider delegates. This is not a complete list, but gives you a pretty good idea.
What it doesn't give you: RN license, CNA license, LPN license.
CPT is a Certified Phlebotomy Technician. This allows you to perform blood draws in various locations that require this specialty certification eg: Hospitals, labs, draw stations, blood banks, etc...
CPTs alone cannot perform the duties of a medical assistant if this is the only certification held.
CET is a Certified Electrocardiogram Technician and allows perform EKGs, stress tests, holter and cardiac event monitor testing, telemetry, take vitals, work in cardiac testing facilities and hospitals.
CMAA is a Certified Medical Administrative Assistant that primarily focuses on front office, billing and scheduling duties.
CBCS is a Certified Billing & Coding Specialist. This certification is primarily used for the billing of procedures to the insurance company for reimbursement.
CEHRS is a Certified Electronic Health Records Specialist who specializes in the implementation, management and optimization of electronic health records in a healthcare setting.