Updated: Jan 10, 2022
Heavenly Stems in the Bazi chart always written on the top row of the chart.
It shows the "characteristic" that outer world can see about you.
When it combines, it will also create another strong characteristic. This combination can be found in the Natal chart or Luck Pillar ( the set of 10-years that represents circumstances, chances, experiences, etc) or Annual Pillar.
And when it clashes, you may check which elements that clash or to be clashed.
Whether its combine or clashes, both only tell us that there will be some kind of changes happened -- means uncomfortable feelings also will form.
The difference is on the clash - especially being clashed - we aren't ready for the change and try to go against it and can create pain.