If you talk to a technical person about Wi-Fi then eventually the subject of 2.4GHz comes up along with a list of issues. The root of this goes back to the early days of Wi-Fi and how wireless spectrum was allocated. Wi-Fi currently operates in two frequency bands – 2.4GHz and 5GHz – however until recently the vast majority of devices and equipment only operated in the 2.4GHz spectrum, this was due to early aspects of licencing and manufacturing which meant a rapid adoption of 2.4GHz and a much slower rate of adoption of 5GHz.
The problem is that the 2.4GHz frequency band is not just used by Wi-Fi, it shares it with Bluetooth, baby monitors, various audio & video senders and pretty much anything else that needs an unlicensed frequency band. It is also the frequency that microwave ovens use and yes that can cause problems in kitchens! The upshot is that the frequency band is overcrowded meaning that Wi-Fi is fighting amongst a lot of wireless noise, generally leading to reduced or intermittent performance.
On top of this the actual spectrum available to Wi-Fi at 2.4GHz is very limited – in theory there are 13 channels but in reality only 3 of these channels are usable without causing interference to other channels which makes it very difficult to design large scale deployments. The situation is so bad on event sites that 2.4GHz can be almost unusable. The good news is that most mobile device manufacturers have increasingly incorporated 5GHz support into their devices over the last few years.
Overall the 5GHz band has a much wider spectrum allocated meaning more channels are available and there is less interference from other devices (although RADAR does use 5GHz, as does some metrological equipment). Today 5GHz is much less crowded than 2.4GHz and provides a much better user experience, however, with the widescale adoption of 5GHz in consumer products such as Mi-Fi units the situation is changing so we may well see increasing problems at 5GHz over time.