The British (and Australian and New Zealand) system is somewhat different from the North American one. As I understand it, British PhD programs are almost entirely research focused. There is no requirement or expectation that the grad student teach. Also, most North American schools have some kind of breadth requirement in coursework and examinations before the student starts to work on their dissertation, so the student engages in topics outside their research field. And when you apply to a British program, you do apply to work on a specific project. As a result, the nominal completion time for a British PhD is three years, as opposed to five in North America. Some claim that this results in lower-quality research. I don’t believe that to be the case, but there’s no question that those who emerge from North American PhD programs have a broader range of skills and are better prepared for the job market than their narrowly focused British counterparts.
There are also big differences between the disciplines. A humanities PhD program takes a very different shape than an engineering or sciences one, both in the requirements and how they’re funded.
As an example, here is the nominal schedule for an English PhD student at the University of Toronto. Each school and department will vary, but in broad strokes this is what a North American PhD program in humanities looks like. Canadian schools are also a bit different from US ones in that they generally require a master’s degree for admission. US schools may have more coursework in the first two years.
Year 1: Coursework
Year 2: Comprehensive exams (covering all of English lit); assembling your committee and defining your research project
Year 3: Special field exams (on your chosen field and research topic); candidacy status achieved, begin work on your dissertation
Year 4: Dissertation work
Year 5: Dissertation work, oral defense
Throughout, the student works as a graduate teaching assistant; typically starting with a grading-only TAship in the first year, then moving on to leading break-out groups. Once candidacy is achieved, most students will also serve as instructors in their own right, but that’s over and above the program requirements.
Also, many students will, at some point, work for a year or more as a part-time research assistant for a professor. This work is separate from the program and is funded by research grants acquired by the professor.
This is the nominal trajectory. Pretty much no one follows the plan exactly and most take six to eight years to complete, if they complete at all.