For those words in english which sometimes have two passed tenses ?

see
seen
saw

sing
sang
sung

eat(en)
ate.

writ(en)
wrote

I can't think of any rules as to why i would use one over the other, and i dont know how i would ever explain this to a russian if they asked. Does anyone know ?

Is it a british / american english thing ? like Theater, Theatre ? lol, i dont know.