If the first number of the subject code is 1, then it is a level 1 subject, if the first number is 2, then it is a level two subject etc etc
So a subject like Accelerated Mathematics 1 has the code MAST
10008
Since the first number of the subject code is 1, it means it it a level one subject
Something like Quantum Systems has the code PHYC
30020
Since the first number is a 3, it means it is a level 3 subject
Levels may indicate the difficulty of the subject (i think)
Usually you may have to do a level 1 subject or two to satisfy the prereqs of a level 2 subject, and a level 3 subject may need a level 2 subject as a prerequisite
https://handbook.unimelb.edu.au/faces/htdocs/user/search/AdvancedSearch.jspTo search for all level 1 subjects, just go to the section in the top right corner, and where it says 'Level' enter 1
Then you can choose the study areas etc etc