The difference is about Bluetooth & Bluetooth Smart (aka Low Energy). The second one is in fact a different protocol, once called Wibree, which uses some parts of the Bluetooth stack, but not a lot of it. While Bluetooth "Classic" already has network connectivity through PAN since a long time ago, Bluetooth Smart, introduced in the 4.0 revision of the specification, does not.
The main reason for this is that the maximum packet size in Bluetooth Smart is quite small (around 256 bytes in the original spec). The latest revision allows for higher MTUs, as well as an IPv6 header compression scheme called 6lowPAN, already developped for IEEE802.15, another low energy radio protocol.