Jenna - the gear changing is really simple - all you are doing is cutting out the intermediate ones that you've effectively eliminated by slowing down using your brakes. Ask your driving instructor to explain engine revs and driving speed/conditions to you, then it will all make sense ! For instance, you are driving along - straight road, national speed limit, single carriageway, no obstructions, good visibility and road conditions.... hence max driving speed of 60mph in say 4th gear... then you come to a bendy bit of road, poor visibility, steep incline... you obviously have to brake (or take your foot off the accelerator) but since the road ahead is still bendy and steep and with poor visibility... by going down to 2nd gear you are ready to approach the next bend in a safe and controlled manner, rather than trying to go down into 3rd and then a few seconds later down into 2nd gear.... this will slow you right down with no need to brake and you are in the correct gear for the road conditions !
Oh, back to the Question... I wish I could work out the subtle nuances of Cat ....