Glop and Sandite are the same thing. 'Sandite' is the correct term, 'Glop' is a nickname, so called because of its consistency. It is a solution applied to the railhead during low adhesion to improve grip and keep track circuits operating.
Market lights are the basic lights on a train. Like parking lights on a car.
For the TRP test you'll be given a case study involving one or the other of these two. You'll read about each subject and make notes. youll then have time to go over your notes before they are taken away and you are given a test on what you've read.
It follows that the human brain is only capable of remembering about 7 or 8 things in the short term memory. So my advice would be to list keywords in your notes that will serve to jog your memory in the test.