All students of Biology at some stage address the topic of Digestion, with its diagrams of organs and the enzymes they produce to break large molecules like starch down into smaller molecules such as sugars.
Most will regard this stuff as so much detail to commit to memory - at least temporarily - and in order to do so may go over it a number of times: to digest Digestion as it were.
In Maths and Sciences the agenda for purposeful GCSE revision is set out in defined topics such as 'Digestion', each with its breakdown of facts, relationships and methods. The kind of student at whom this is aimed is not expected to find any particular topic hard in itself, but will be challenged by the quantity of principles, ideas and details to be learned for each examination.
Making a late start on revision, and so having to swat and cram for multiple papers of Maths and Science, is not recommended. (If you are in this situation I suggest you
concentrate on the selection of topics you find more interesting and less difficult to understand!)
With English the situation is clearly different; English Language doesn't lend itself to an easy break-down into discrete topics - revision is more problematic, and some students may consider therefore that revision is not as purposeful or necessary for English as for other subjects.
This is what I shall consider in my next post ...