The e3-12xxv2 is Ivy Bridge LGA1155 socket.
The e3-12xxv3 is Haswell LGA1150 socket.
The e3-12xx is Sandy Bridge LGA1155 socket.
The last two number like e3-1230, 1240, 1245, 1270, 1275, etc... indicate differences in clock speed. The models that end in 5 have integrated graphics.