Alivio (M4000) is on their website, on the MTB Groupset page. Here's the Alivio M4000 specific page.

The significance with Alivio M4000 is the Shadow technology in the rear derailleur. As far as I know, it's the "lowest" of Shimano's hierarchy with this technology. More about the benefits of Shadow are on Rideshimano.com.

I've used both SRAM and (traditional) Shimano, and I really prefer SRAM's style of rear cable routing and specific chain tensioning design (which differs from traditional rear derailleur design). Shimano's Shadow derailleurs are closer to SRAM's design than their traditional designs. I'm glad to see them going this way, because I think it's a superior design. Its roots are in MTB, but there are few downsides that I'm aware of, even for city/hybrid bikes like what we ride.