Push is the more efficient way of delivering data to the client application; this service is synonymous with the BlackBerry experience, where it has been used for delivering emails and BlackBerry Messenger messages since the beginning.
For anyone who does not yet know what Push is, here is a brief overview in comparison to a couple other ways of invoking data:
1) Pull – Request all data all the time
a. Not efficient (battery and bandwidth-wise)
b. Info may be available to client well before pull
c. Client application needs to be running
2) Poke – Message the server and ask if new data is available, pull if available
a. Info may be available to client well before poke
b. Client application needs to be running
3) Push – The server sends the client new data as soon as it becomes available
b. Data is immediately available to the client
c. Client application does not need to be running
To inquire more into how to implement Push, check out the article by Garret from the InsideBB Dev blog.