The U on iTunes - Terms
Aggregator
An Aggregator is a client software
that uses a web feed to retrieve syndicated web content such
as blogs, podcasts, mainstream mass media websites, and vlogs.
Aggregators reduce the time and effort it takes to update websites.
Once you subscribe to a feed, an aggregator is able to check
for new content at user-determined intervals and retrieve the
update. iTunes will act as an aggregator when users sign
into the iTunes U portal and then can subscribe podcast feeds.
In the future development their will be an aggregator for other operating
systems, such as Linux, and Unix.