It's not all that complicated. There are three exams, first an entry exam, then a tasting exam, and then down the road a written exam. And then there's experience points, judging points and non-judging (ie stewarding, comp organizer, comp staff, etc).
Basically to enter the program, pass the online entry exam.
Provisional: Pass the entry exam, haven't taken the tasting exam.
Rank Pending: Taken tasting exam, haven't gotten results back yet.
Apprentice: Took tasting exam and failed it (<60%)
Recognized: Tasting exam score 60-70%, or 70%+ with insufficient experience points
Certified: 70%+ on tasting exam, 5 points (half of which must be judging)
National: 80%+ aggregate (average rounded up) score between tasting exam and written exam, 20 points (half judging)
Master: 90%+ aggregate score, 40 points (half judging)
Grand Master: 90%+ aggregate score, 100 points (half judging) plus service to the BJCP (officer roles, exam grading, things like that). And then GM can go up levels itself with additional blocks of 100 points and more service to the org.
See? Easy.