As an common law corporation that's over 800 years old, Cambridge has some interesting rules and regulations; some are mostly archaic and obsolete while others are still relevant and useful today. I use this page to document common gotchas and gems that I find in the S&O, which can canonically be found here. Yes, I'm afraid I do actually care about these, but then somebody has to...
Cambridge University (as opposed to its individual colleges which are completely seperate legal entities) is governed by three different types of rules, Statutes, Ordinances and Special Ordinances. Proposals to change the Statutes have to be approved by an Order-in-Council, that is to say by the Monarch on advice from the Privy Council. Changes to Ordinance or Special ordinance need only be approved by grace of the Regent House, which is comprised of senior university staff.
The definitions of these two terms are given in Section 2, Chapter 10 of Statute A. Put simply a 'registered student' is someone who is studying and hoping to obtain a degree, certificate or diploma from the University. Conversely 'in statu pupillari' has a much more complicated definition: a member of the University (or someone about to matriculate) who is not a member of University or Collegiate staff, who is not a member of the Senate and who is of less than three and a half years' standing from admission to their first degree, if any. Put simply, this means that i.s.p. includes current students as well as recent graduates who have yet to receive their Cambridge M.A.
Regardless of the technical minutiae here, 99% of the time that someone uses the term 'in statu pupillari' what they really mean is 'registered student'. Please use 'registered student' and not 'in statu pupillari'. I note the the University itself is often guilty of this.
These days the Senate has very little power. In practice, it exists mostly to rubber-stamp nominations for the positions of Chancellor and High Steward, though the S&O do lay out a variety of other theoretical powers it could exercise. Under Chapter 1 of the Ordinances, members of the Senate can form a part of the Nomination Board for Chancellor and High Steward elections. In theory there should be sixteen places on the Board for members of the Senate, four appointed each year by Grace of the Senate on the nomination of the Council, however the exact numbers tend to vary somewhat; elections don't happen all that often so this likely isn't seen as a priority. Fifty or more Senate members may also submit a nomination directly to the Vice-Chancellor, bypassing the Nomination Board, as (in)famously happened the last time the position became vacant in 2011.
The Senate also has the power to enact Graces, though they may only be submitted to the Senate with the approval of the Council. They are submitted by being formally published in the Reporter and are de facto approved unless a ballot is called for by ten or more members of the Senate. Do not confuse this process with that used by the Regent House to enact Graces which is similar yet distinct.
Discussions are the primary means by which members of the University feedback their views to the Council. They usually occur on about a weekly basis, with notice given in the Reporter. Though this list may be varied by Grace, at the time of writing Discussions may be attended and participated in by members of the Regent House or Senate, graduates of the University, members of Faculties, registered students & sabbatical officers of the Students' Union and anyone else who the Vice-Chancellor may authorise on an ad-hoc basis to attend a particular discussion. Discussions are not debates, but rather an opportunity for support, disagreement and comments to be recorded officially. Speeches are written before hand and read out, either by the person themselves or by a Proctor on their behalf, but they must be less than fifteen minutes in total length. The text of the speech will then be published officially in the Reporter by the Registrary.