First of all, a doctor is a degree and a doctor is a professional title. Ph.D is short for DoctorofPhilosophy. A research degree usually requires a certain degree of course study and thesis writing. People with doctoral degrees can engage in research and teaching in academia, research institutions or enterprises.
Doctor is a general term used to indicate that a person has a doctorate. In the United States, only people who get a doctorate can be called Dr. However, in Britain and some other countries, people can use this title to show that they have a doctorate, even if they don't.
Secondly, a doctorate usually takes longer to complete. In the United States, most schools require students to complete their doctoral studies and thesis writing within five years. However, in some cases, students may need longer time to complete their research projects.
In addition, doctorates usually require higher standards. In the United States, most schools require students to pass a comprehensive exam and submit a high-quality paper before completing their doctoral degrees. These requirements are aimed at ensuring that people who have obtained doctoral degrees have solid research ability and professional knowledge.