Our fathers worshipped on top of this mountain.
Набототи сайёраи мо хеле гуногун аст.
The plant life on our planet is very diverse.
In our two sentences мо is a possessive adjective, our. But мо can also be used as a pronoun. No need to learn lots of different words like in English!
мо: we, us, our, ours
Мо рафтем. We went. (personal pronoun, subject of the sentence)
Онҳо моро диданд. They saw us. (personal pronoun, object of the sentence)
Ин аз они мо нест. This is not ours. (possessive pronoun)