Entry into US....confused

I have heard conflicting stories on the interview for request for green card.
I have heard that they will stamp your passport that day and then you will recieve your green card in the mail 2-3 months later.
I have also heard that they will not stamp your passport until you get your greencard.
Does this mean that after the interview you are not allowed to travel out of the US for the chance you may not get in. But can you travel if they do stamp your passport that day?
Confused?
Help!

I have heard conflicting stories on the interview for request for green card.
I have heard that they will stamp your passport that day and then you will recieve your green card in the mail 2-3 months later.
I have also heard that they will not stamp your passport until you get your greencard.
Does this mean that after the interview you are not allowed to travel out of the US for the chance you may not get in. But can you travel if they do stamp your passport that day?
Confused?
Help!

well one thing is definitely sure here...you absolutely cannot travel if yr passport hasn't been stamped...

If they stamp your passport the day of the interview, that means you have been approved for a greencard, which probably comes in the mail shortly thereafter. In this scenario since you are approved and stamped you can travel.

If they do NOT stamp your passport that day it means they have not yet approved you for a greencard. Maybe they are waiting for results of the background check, or need other information first. In that case, you are NOT yet approved and CANNOT travel.