SharedObject

I have two points firstly…I have been watching some tutorials in regards to SharedObjects. I still however, find it difficult to distinguish the getLocal()Method and Remoth SharedObject. If someone can explain the main difference from the two and tell me what their primary purpose is i would appreciate it.
My second point if your in a chat room for example. Where two users are sending messages back and forth to one another. And you want to store the data that the users have been exchanging can you use the SharedObject method to store the data