These abbreviations may confuse patients. I am a PTA, a Physical Therapist Assistant, and commonly receive questions often about the differences between these titles.
A Physical Therapist, a PT, is a licensed healthcare professional that completed a graduate program to help patients reduce pain and restore or improve mobility. A DPT, Doctor of Physical Therapy, is now the entry level for the professional degree for physical therapists. A PTA, Physical Therapist Assistant, is an associate-degreed and licensed healthcare professional that works under the direction and supervision of a PT.
A physical therapist assistant can not evaluate a patient nor can they sign a discharge note. A PTA can not establish an initial plan-of-care based on patient evaluative diagnosis nor can we set-up their goals. We 
can however, work closely with the PT to address any changes that need to be made to patient goals or their plan of care, all with the best interest of the patient in mind.
PTs or DPTs and PTAs work as a team for the best patient outcome of pain free living and/or help to return patient to prior level or highest level of independent living for everyday activities. The procedural mechanics of the human body, proper therapy interventions, etc. are learned both through both the PT and PTA educational programs.
A Physical Therapist Assistant (PTA) is not a bridge program nor are these therapists “currently studying”, “on the path to”, nor “furthering” themselves to become a Physical Therapist “some day”. These are two different paths in the physical therapy world. Most generally an individual will choose the field that fits them best. For me, I chose PTA because working closely with a person in their path to healing is important and what drives me. I love what I do and am happy I chose to become a Physical Therapist Assistant!
Listed below are websites that provide more detailed information from as well as a “V.S.” blog from Methodist regarding this same question for your reading pleasure.
https://blog.methodistcollege.edu/pta-versus-physical-therapist-whats-the-difference
https://en.wikipedia.org/wiki/Doctor_of_Physical_Therapy
http://www.apta.org/AboutPTs/
