Tent is data-agnostic. All your data is stored as posts in your account on your Tent provider's server. Posts can be private or public, you decide who gets access to what.
Other Tent users may subscribe to your posts (the ones they have access to), and your Tent provider will then push any new posts you create to your subscribers. You subscribe by specifying what type of data you're interested in, and receive only posts matching that query.
This is in contrast to the web, where the browser usually goes out and actively fetches data from a server (i.e. pull). Tent's push model has many advantages and opens up some interesting possibilities for developers. Even so, it's not going to replace the web any time soon, but rather compliment the web in the areas where it comes up short.
Tent is a protocol that operates alongside the web and email, as an alternative decentralized and secure communication channel on the Internet.