Connection Mode shows the type of connection / type of WLAN , such as 802.11n, 802.11ac, 802.11ax etc. Your screenshot shows that the AP radio is 802.11bgn, which means, it uses the 2.4 GHz frequency.
802.11b supports 2.4Ghz.
802.11g & n can support 2.4Ghz or 5Ghz or Both.
802.11a & ac support only 5Ghz.
Since this is a client session report, I think the client devices are using the 802.11bgn wireless NIC card.