sentient

Guru Fateh! In some Gurbani discussions I have been hearing references to something called chetan and a concept of "sentient vs. non-sentient" parts of being. I cannot find references to this in Gurbani and I can't find the word chetan. I also have been doing google searches to try...

i think most every can agree that plants are alive... but are they sentient? are there beings (other than Buddhas) that aren't sentient and thus can't reach enlightenment (in a future rebirth) or aren't effected by samsara?