Short answers, pulled from the story.
Oxbridge is a portmanteau of Oxford and Cambridge, used to refer collectively to the two oldest, wealthiest, and most prestigious universities in the United Kingdom. It also carries broader connotations of elite social and intellectual status.
The Oxford English Dictionary credits Virginia Woolf with the first recorded use of Oxbridge, in her 1929 extended essay A Room of One's Own. She was citing an earlier appearance in William Makepeace Thackeray's 1850 novel Pendennis, where the fictional Boniface College, Oxbridge is named.
Oxford and Cambridge are almost always named in that order because it reflects the sequence in which they were founded. Tokyo's Cambridge and Oxford Society is a notable exception, reversing the names because the Cambridge Club was established there first and had more members when the two merged in 1905.
The tutorial or supervision is the main undergraduate teaching method at Oxford and Cambridge, and is unique to those two universities among UK institutions. It involves one-on-one or very small group meetings between a student and an academic to work through material in depth.
A Sutton Trust analysis of admissions data from 2015 to 2017 found that eight schools accounted for 1,310 of the 19,851 places over those three years. Those schools were Westminster School, Eton College, Hills Road Sixth Form College, St Paul's School, Peter Symonds College, St Paul's Girls' School, King's College School, and Magdalen College School.
Several portmanteaus have been coined on the Oxbridge model. Loxbridge refers to the London, Oxford, and Cambridge triangle. Doxbridge adds Durham. Woxbridge combines Warwick, Oxford, and Cambridge. When St Andrews topped The Guardian's 2023 UK university ranking, the top three institutions were labelled Stoxbridge.