The very simple version is that the newer versions support faster speeds.
I would add the potential for better range as well from a variety of improvements.
Newer WiFi standards can take advantage of multiple frequencies in a single link, which allows for fallback on the slower, but longer range, 2.4GHz networks. Beamforming has been available since at least WiFi 5 (802.11ac) and helps connection quality as well. The new 6GHz spectrum is uncongested and gives better performance in areas with high saturation of 2.4GHz and 5GHz networks, such as apartments and highrises.
Range is definitely not better with 6. 6 has larger bandwidths, and is less congested right now because of all the IoT devices using 2.4 and 5 Ghz bands. This will change eventually. 2.4 still has the best range.
WiFi 7 (802.11be) has Multi-Link Operation (MLO) where it uses both 6 GHz, 5 GHz, and 2.4 GHz frequencies simultaneously to always maximize bandwidth at a given range.
