RADIUS: starting accounting session

Seeing some times when devices connect: RADIUS: starting accounting session, what is that?

Mon Sep 13 16:31:30 2021 daemon.notice hostapd: wlan1: AP-STA-DISCONNECTED c8:c7:50:xx:xx:xx
Mon Sep 13 16:31:30 2021 daemon.info hostapd: wlan1: STA c8:c7:50:xx:xx:xx IEEE 802.11: authenticated
Mon Sep 13 16:31:30 2021 daemon.info hostapd: wlan1: STA c8:c7:50:xx:xx:xx IEEE 802.11: associated (aid 2)
Mon Sep 13 16:31:30 2021 daemon.notice hostapd: wlan1: AP-STA-CONNECTED c8:c7:50:xx:xx:xx
Mon Sep 13 16:31:30 2021 daemon.info hostapd: wlan1: STA c8:c7:50:xx:xx:xx RADIUS: starting accounting session 00A3Bxxxx42E45
Mon Sep 13 16:31:30 2021 daemon.info hostapd: wlan1: STA c8:c7:50:xx:xx:xx WPA: pairwise key handshake completed (RSN)
Mon Sep 13 16:31:30 2021 daemon.info dnsmasq-dhcp[5231]: DHCPDISCOVER(br-lan) c8:c7:50:xx:xx:xx
Mon Sep 13 16:31:30 2021 daemon.info dnsmasq-dhcp[5231]: DHCPOFFER(br-lan) 192.168.1.22 c8:c7:50:xx:xx:xx
Mon Sep 13 16:31:30 2021 daemon.info dnsmasq-dhcp[5231]: DHCPREQUEST(br-lan) 192.168.1.22 c8:c7:50:xx:xx:xx
Mon Sep 13 16:31:30 2021 daemon.info dnsmasq-dhcp[5231]: DHCPACK(br-lan) 192.168.1.22 c8:c7:50:xx:xx:xx smartphone