Your HSC marks (final marks) across your subjects are used in the calculation of your ATAR. An HSC mark is comprised of an Assessment Mark worth 50% and an Examination Mark worth 50%, meaning that in order to calculate an HSC mark, the average of the Assessment Mark and the Examination Mark is calculated.
The Examination Mark refers to the mark you receive in the HSC exam (external) of a particular subject. This mark depends on your own performance in the HSC exams (i.e. it is not affected by factors such as your rank relative to your cohort in a particular subject or your school rank) and is subject to alignment.
The Assessment Mark refers to the mark you achieve in a particular subject based on your performance in your school-based assessment tasks/exams (internal). It is determined through a process called moderation, which uses Examination Marks achieved by your cohort to adjust students' Assessment Marks. You may be aware that ranking is an essential part of your performance with respect to the Assessment Mark, meaning that in order to maximise your Assessment Mark in a particular subject, you will need to rank as highly as possible relative to your cohort, which can only be done by performing to the best of your abilities in your school-based assessment tasks/exams.
Essentially, the highest Assessment Mark is adjusted to equal the highest Examination Mark of any student in a school cohort. Similarly, the lowest Assessment Mark is adjusted to equal the lowest Examination Mark of any student in a school cohort. In the case of other ranks, the Assessment Mark will not equal its equivalent Examination Mark. However, it will be similar. Consider the following example from NESA:
As you can see, the highest Assessment Mark was adjusted to equal the highest Examination Mark (92). The lowest Assessment Mark was also adjusted to equal the lowest Examination Mark (50). However, the Assessment Mark for the student ranked third (74) is not identical to the third-highest Examination Mark (72), although it is similar.
The Assessment Mark is also subject to alignment, similar to the Examination Mark.
I hope this helps!