The specification has multi-station throughput of at least 1 gigabit per second and single-link throughput of at least 500 megabits per second (500 Mbit/s).
This is accomplished by extending the air-interface concepts embraced by 802.11n: wider RF bandwidth (up to 160 MHz), more MIMO spatial streams (up to eight), downlink multi-user MIMO (up to four clients), and high-density modulation (up to 256-QAM).
The 802.11ac second wave is more mature. With improved hardware, 802.11ac moves up to the 5 GHz band where it can offer mandatory 80 MHz and optional 160 MHz channels.
802.11ac beam forming is a big improvement which will improve throughput with multiple access points service an office etc. Unfortunately many non-compliant 802.11n devices do not properly support beam forming.
Using multiple antennas and borrowing from phased array radar technology will improve performance for each user in a coffee shop. The multiple antennas electronically steer the beams. This gives each user more bandwidth that is possible with 802.11n.
A mobile phone with 1T1R will achieve 433 megabits per second. A 2T2R can achieve 867 megabits per second.
Clearly up at 5 Ghz there is a lot more bandwidth. The span for 20 MHz channels is vast which is why we strongly recommend abandoning 2.4 Ghz completely. 802.11a, 802.11n and above all support 5 Ghz.