"This is a Samsung Galaxy S4 with the same software experience we ship on our Nexus devices. It's Google's take on Android and it feels awesome on the S4," said Google VP Hugo Barra.
It's good news for everyone. Google can sell a powerful LTE phone that doesn't compete with Nexus 4 because it's more expensive. Samsung has access to Google's software updates, so there's less work to keep up with the new Android versions. Developers can buy a Nexus version of the most popular Android phone and can even use a MicroSD card, replace the battery, use a physical home button and two other capacitive buttons. People who want to buy a Galaxy S4, but don't like Samsung's TouchWiz software, no longer have to rely on custom ROMs. Projects like CyanogenMod will do a better job of supporting Galaxy S4. Even if you buy the regular Galaxy S4, you'll get better software, whether you stick with Samsung's software or you install a custom ROM.
Samsung manufactured 2 other Nexus phones (Nexus S - 2010, Galaxy Nexus - 2011) and a Nexus tablet (Nexus 10 - 2012).