Unless you happen to be part of the academic system, how an academic career actually develops is not widely know or understood. To be honest, even to those within the system, the whole thing is pretty damn confusing. It is possible to skip certain steps, ‘fellowships’ pop up at all different levels of the career path, and despite having the same label have completely different meanings, and the differentiation of ‘levels’ is often ambiguous.
To clear this up I have made a pretty picture and given a small description of each stage. To be clear though, my picture is a fairly linear simplification of the system, and alternative pathways with roundabouts, traffic lights, and holes in the ground all exist. In addition, I am talking solely about the UK system. In the rest of the world requirements differ and titles of positions vary: though the general pathway of undergraduate degree, to postgraduate degree, to post-doctoral research, to an academic career, hold true. Furthermore, this is written from the perspective of a scientist (specifically a chemist), and in the arts this is probably quite different.
(y = years)
A BSc (Batchelor of Science) and MChem (Master of Chemistry) are primarily taught courses requiring the learning of material and the succesful completion of examinations. These qualifications are graded as 3rd class (3rd), lower 2nd class (2:2), upper 2nd class (2:1) and first class (1st), with a 1st being the highest level.
A BSc and MChem are typically identicle for the first two years. The second two years of an MChem are more research focussed than the final year of a BSc, and taught modules in the final year of an MChem are of a level beyond that of the BSc. An MChem is a higher level qualification than a BSc.
MSc (Master of Science), MRes (Master of Research), MPhil (Master of Philosphy) are postgraduate degrees of the same level. The proportion of research and taught modules differentiates each qualification. Completion of examinations and submission of a research thesis is required for completion of the qualification. The qualification is graded using a pass/merit/distinction scale.
A PhD (Doctor of Philosophy) is typically 100% research based and is completed over a 3-4 year period. A PhD student will research a specific topic(s) over a number of years under the supervision of an academic (university lecturer), and is then required to submit an extended thesis (200-300 pages) reporting this work. For a PhD to be awarded the student must defend their research, which has been critically evaluated by two academics (university lecturers) in an oral examination (viva) lasting for 2-4 hours. PhD research must be of a publishable level i.e. of a quality that could be submitted to peer-reviewed journals for publication in scientific literature, but publishing research is not a requisite for completion of the qualification (though is highly desirable). A PhD is not graded on a sliding scale, though successful completion of these studies affords the student the title of Dr.
Post-doctoral research (or “post-docking”) is not a formal qualification, but is typically required for progression in an academic career. Post-doctoral research is completed under the supervision of an academic in a manner similar to a PhD, but a significantly increased level of independence is expected, and the ability to generate ideas and develop this into publishable (peer-reviewed) research papers is critical. Post-doctoral positions are typically between 1 and 2 years, and a number of these may be undertaken in different research groups (i.e. working for different academic supervisors) before moving up the career ladder. Undertaking a post-doctoral research position under the supervision of your PhD supervisor is not generally viewed as favorable.
A position as a lecturer or an independent research fellow is the first position in which you are regarded as independent scientist (an academic). You are no longer working under the supervision of another academic, and at this stage you will often begin to supervise PhD students and potentially employ post-doctoral researchers. As well as undertaking and publishing your own research, teaching of undergraduate and post-graduate students is often a requirement of employment. A position as a lecturer is slightly favourable as the position is typically permanent, a luxury not afforded to independent research fellows.
Career progression from a lecturer through to a professor is neither essential or guaranteed. Progression through the ranks typically reflects your contribution to your subject in terms of research (and to a lesser degree teaching). Teaching requirements typically reduce throughout the career path, though the best academics (in my opinion) typically maintain as a high a commitment to teaching as possible. A successful research career is often reflected in an academics ability to procure financial backing for their research ideas, and the successful implementation of these ideas (demonstrated by publishing research). As a consequence, more senior academics typically have more financial support and thus employ more post-doctoral researchers and supervise a greater number of PhD students. The writing of research proposals to procure funding is one of the most significant administrative requirements of an academic.