Yes, 4G mobile networks are different than 3G+ networks. 3G+, also sometimes called 3.5G, is an evolution of the HSDPA (High Speed Downlink Packet Access) mobile broadband network standard. 3G+ delivers faster download speeds, up to 21 Megabits/second. Some operators have evolved to this faster technology as a middle stage before moving to the all IP-based 4G LTE network.

4G, marketed today as 4G LTE, is an all-IP based network, and much faster than its predecessors with download speeds of up to 100 to 128 Megabits/second. Much higher network capacity and speeds mean better quality voice and data services, as well as high-definition video capabilities.

See also,

What is Long Term Evolution?

What is 4G?

How much faster is LTE on the iPhone 5 compared to 3G on the iPhone 4s?

What is a UICC and how is it different from a SIM card?