What does "P. S." means and stands for in emails and letters?

P. S stands for post script.

P. S means a small short little ending for when a letter or email or message is done.

Ex: Lets all go shopping at the city mall. We'll have so much fun.

PS: Don't tell your little brother we are buying ice cream! : >)

It means post script. post means after thats why we use it after the message or letter for additonal information