HeadbuttHigh and HeadbuttLow

[LordHypnos]

This is a very simple question, I'm even a bit ashamed to ask but I really want to know:

What is the exact difference between HeadbuttHigh and HeadbuttLow and do I need to define encounters for both methods or is one enough?

I don't really understand what the wiki means when it says "common" or "rare".

 

[Radical Raptr]

You're more likely to see common than you are to see rare

 

[FL]

The headbutt encounters have a very weird formula. Check at: https://pokemonessentials.wikia.com/wiki/Talk:Encounters