difference between uttam purush vachak sarvanam and pratham purush vachak sarvanam!

can you please explain sarvanam in simple words along with a few examples?? Thank you.

hindi grammar:

"ये घर मेरा है" -choose सर्वनाम (plz note dere is only 1 pronoun- doubt between "yeh" n "mera")......answer ASAP.

what is