Two ways to trigger it: timed (via Settings) and ad-hoc (via a software button in a separate Mobile Settings app).
When suspend is triggered, the screen turns off. (You can tell it’s suspend because the phone cools down considerably after a while.) Calls and SMS will wake it up but other events won’t. Waking up with the side button is instant, but it takes a few seconds until wifi and mobile data come up again.
Mobile data comes back up pretty much instantly, it's just WiFi that takes some time. For the record, WiFi connects back very fast after switching NetworkManager to (experimental) iwd backend instead of wpa_supplicant, but it breaks WiFi-based location because Geoclue only knows how to talk to wpa_supplicant.
Two ways to trigger it: timed (via Settings) and ad-hoc (via a software button in a separate Mobile Settings app). When suspend is triggered, the screen turns off. (You can tell it’s suspend because the phone cools down considerably after a while.) Calls and SMS will wake it up but other events won’t. Waking up with the side button is instant, but it takes a few seconds until wifi and mobile data come up again.