The technical term for the various wireless standards is 802.11 and a letter which were G, N and now AC. If you get the current standard you want 802.11AC. However, the actual names of the IEEE standards for wireless (802.11) is not very clear to the average user of wireless.
Often people knew them by the letter. Now the association over wireless has come out with numbers to hopefully make clearer. AC is version 5 in their numbering and N is 4. There is a newer standard that has not adopted yet (partly that devices must be so close the wireless access point) that is AD or 6.
If you buy a wireless access point (sometimes referred to as a router, but really more a switch and actually an access point) you want to get AC
Prior to AC most wireless standard had the transmissions on the 2.4 ghz range. AC uses the 5 ghz range mainly but does some stuff in 2.4. A problem with the 2.4 ghz range was a lot of other devices (including microwaves) use that frequency and there was lots of interference in the air and slowed down the effective speeds. Oddly enough originally in wireless there were two standards A and B and a used the 5 ghz and B used 2.4. B was the one that caught on.
AC works on the approach of it uses 5 ghz (which has higher speeds) for devices closer and when they get to far for that 2.4 works and they will change connection to 2.4 ghz. Likewise, if the device gets closer it will move up to 5ghz.
AC has rated speeds that could in time be up to 3gbps although high of speed not available now. N worked at up to 600mbps, so AC is about 5 times faster.
AC is backward compatible with B, G and N so if you get a AC wireless access point and still have B, G and N devices they will all work together, although the slower devices will work at slower speeds.
If you are shopping make sure the wireless is AC or 5. Before you do but check and see if the router supplied by your ISP includes wireless as many do now and you may already have your wireless needs met. If not make sure that they do not have one for you at no additional cost to get the whole Internet signal at the best speeds.