What happened at the end of Pretty Little Liars?

Answer 1

At the end of Pretty Little Liars you find out that when Aria, Spencer, Hanna & Emily knew "Ali" it was actually her insane twin Courtney pretending to be her. Ali is sent away to the mental hospitals instead of Courtney and when Ali gets back from the hospitals because she's improving, she kills Courtney by shoving her in the hole. When "Ali" (actually Courtney) doesn't come home they assume the twin at home is Courtney and that she killed Ali. So they send "Courtney" (actually Ali) off to the mental hospitals again. Then in the last book, the real Ali (who everyone thinks is Courtney) gets out of the hospital and befriends Hanna Spencer Aria and Emily again, telling them that she is actually Ali. Then she takes them up to her Poconos house and writes everything I just did to them in a letter and sets the house on fire. Luckily, they all get out saftley, except Ali who dies in the fire.

Answer 2

Alison murders her twin sister, leaves town for a bit, then comes bak in hiding
Its currently not known. 2013 the series will end.