WIFI common concept

802.11b(2.4G)
802.11g(2.4G)
802.11a(5G) old 5G
802.11n- HT( or Legacy 2.4G)
802.11ac -VHT(5G)
802.11ax -HE(5G)

When people talk about
When people talk about 5G we will refer to 11AC and 11AX.
Some people will use
11AC as VHT
11AX as HE
11N as VHT or Non-HT（Legacy）

BandWidth:
2.4G: 20,40 MHz

5G: 40,80,160 MHz