cjjc:
jesteś - You are
jestem - I am
so far so good.
Not you, that is Jesteś
ono jest = he is
Ona jest = she is
On jest = it is
You should take them all together so you can see them and see the similarities with all the other verbs. This is the simple version (not too much gender involved)
I am Ja jestem
you are Ty jesteś
he is Ono Jest
she is Ona Jest
it is On jest
we are Wy Jesteśmy
youz are Cie Jesteście (in Irish English we youz for you plural)
they are Oni są
For example if there is an Isalnd with a billion women on it we say "Oni Są"(they plural female are) if you put one man on the same Island with the billion women it becomes "One są" (they plural male are).
I asked a friend why it all changes, she quickly replied a billion women and one man, this changes everything;)