I think detlier's description is pretty clear. What we said is the timer that the SoftAP found the STA has been out of range or power off.
You can reproduce this issue by the following steps easily:
(1) Use two ESP32 devices, one is as SoftAP, the other is as STA
(2) STA connects to the SoftAP
(3) Power off the STA. But The SoftAP doesn't know this , so it will wait for 5 min, if during this time ,the SoftAP doesn't receive any messages from the STA, it will kicks out the STA, and print the log for inactive timer:
W (552929) wifi: inactive timer: now=20f010f1 last_rx_time=ef8bad1 diff=4996e, aid[1]84:3a:4b:9e:64:c0 leave
I (552929) wifi: station: 84:3a:4b:9e:64:c0 leave, AID = 1
I (552939) wifi: n:4 0, o:4 0, ap:4 1, sta:255 255, prof:4
I (552939) esp-streamer: station:84:3a:4b:9e:64:c0leave, AID=1