Hsing I is based on 5 basic movements.
Splitting - Up to down - like splitting wood with an axe.
Drilling - forward and aggressive - Like a drill (funnily enough)
Crushing - This is the main power punch of Hsing i - extend and expand powerfully.
Pounding / cannon - fast and destructive, like an explosion.
Crossing - one of the main combat principles - crossing an attacks line of force with your own attack.
These are the 5 basic elements of hsing i - they make up every movement in hsing i. Some schools also have 12 animal forms in the system - this is to teach the different ways of using the five fists and fighting with a set mind - monkey would be passive etc, dragon would be fierce and tearing.
Splitting is used in throwing, Chi na and striking high to low etc
All have their perpose. They are not set techniques but principles / ideas.
Crossing force, crushing force, Splitting force, pounding force etc.
It is not really like western boxing - the mechanics are very very different with different alignment principles etc.
It also contains throwing, locking, limb and joint destruction etc - all of which are not really apparant in Boxing.
hope this helps.