Basically this refers to the order in which you list your courses on the CAO application form. The last date for changing your mind about the courses you have listed, is the 1st July.
It is very important that you list your course preferences in the order in which you genuinely want to receive an offer, and not in the order in which you think you might get an offer, based on the number of points you think you might get.
Because if you get more points than you originally thought, you may not receive an offer on the course you really want to do. Watch this CAO presentation for more details.....