Push technology
Push: a communication protocol - request
comes from the publisher, or central server
Pull: request originates with the receiver, or client.
Examples of push:
- instant messaging (also SMS)
- e-mail (except for last step)
All "true" push media present practical difficulties because the
server is responsible for remembering who the subscribers are,
and
for remembering the latest address that each subscriber should be
contacted at.
Examples of pull:
- web browsing
- RSS (looks like push but aggregator polls regularly so is pull)
Reference: Wikipedia on
push
technology