The best known example of the doctorate degree is the PhD - Doctor of Philosophy. Depending on where you study, you may encounter many variations on what a doctorate entails, what is required and what the aim of you studies is. In general however it can be said that most doctorate degrees are based around the requirement of conducting qualified and original research fit to be published in a recognized research journal.
Doctorates can be loosely qualified in the four following cateogies: Research Doctorate, Higher Doctorate, Professional Doctorate and Honorary Doctorate.
Research Doctorates / PhD
Being awarded a research doctorate requires original research of sufficient quality to be publishable in peer-referred academic journal. Some universities require actually being published, while others merely require the sufficient standard of research. The Doctor of Philosophy, or PhD as it is commonly referred to is the most common and well known version of this degree throughout the world.
The research requirement covers the submission of a substantial body of research by the candidate. This may take the form of either a single dissertation or thesis, or otherwise may also be comprised of several smaller project reports. Assessment is generally conducted by a small committee of examiners appointed by the university.
The layout of PhD programs or research doctorates vary from country to country. In some countries, such as the United States it is also common with a taught component as part of completing the Doctorate or PhD requirement. The minimum time requirement also varies from as little as three years, while some take up to ten years to complete their degree.
Higher Doctorates
Higher doctorates are a higher tier of research doctorates awarded for exceptional research in some countries such as the UK, Ireland and some Scandinavian and socialist block countries. Examples of higher doctorates to be awarded are Doctore of Sciences (DSc/ScD) and Doctor of Letters (Dlitt/LittD) in the UK and Ireland along with Doctors of theology, law or medicine awarded in for exaple Denmark.
Professional Doctorates
Professional doctorates are commonly awarded not for academic research, but for a profession within law, medicine, theology or pharmacy for example.
Professional doctorate can also be used when referring to research doctorates that deal with applied research, which is used for professional purposes.
Honorary Doctorates
Honorary doctorates are awarded by universities to formally recognize someone's outstanding contributions to a particular field or philanthropic efforts. In this case the university waives the formal requirements for awarding the doctorate degree.
Source: http://en.wikipedia.org/wiki/Doctorate
