802.11ac is the current Wi-Fi standard. It uses both the 2.4GHz band (like 802.11b and 802.11g) and the 5GHz band (like 802.11n). The next standard, 802.11ad, is reportedly due this fall and adds a third frequency to the mix (60GHz) and is designed for high bandwidth over short distances.
With 802.11ac as the current Wi-Fi standard, 802.11n-based gear is quite affordable. Naturally, you'll ask yourself whether you should save some money on that older equipment. While you can certainly get acceptable performance from 802.11n, at this point I'd recommend springing for the more modern standard. Much of the early price premium is gone, and 802.11ac does offer some benefits, detailed below.
Within modern 802.11n and 802.11ac Wi-Fi adapters, there are several different speed tiers:
|Type||2.4GHz Mb/s||5GHz Mb/s|
Notice that adding throughput from the 2.4GHz and 5GHz bands gives you the equivalent nomenclature. For example, N600 is precisely the sum of 300 and 300. However, the math is not as clean for AC1200 since 300 and 867 give us a sum of 1176. This gets rounded to a nice even AC1200, which is easier to remember.