Anyone can go to Hulu's website and watch a limited selection of content for free on a computer, but upgrading to the paid Hulu Plus version lets you stream more programs. Hulu Plus also unlocks the mobile apps and set top box streaming, but now the Android app has been updated to let free users get a taste of Hulu on the go.
Free users of the updated Hulu app will get access to recent and past episodes of some shows and a selection of content from Hulu Originals, Anime, Kids, Movies, and Latino. It's basically what you'd get on the free web version, with a few unnamed exceptions.
The other limitation with the free account is that you can't stream to other devices, which I assume means mostly the Chromecast. A few reviews say this is the case, so the free content can probably only be watched on the device itself. Although, I suppose you could screencast (on some devices) or use a cable. Keep in mind making a new account gets you the hard sell with a free one week trial of Hulu Plus, so you'll have to remember to cancel before they charge you.