That is a standard PA announcement which has specific meanings to the FAs. It is used after the FAs have been instructed to take their jumpseats or be seated immediately. Those announcements are over the PA, instead of via the interphone, so that FAs who are not at a jumpseat can hear them. The check in announcement will have the FAs will check in with the purser to report cabin condition, injuries, etc. after an unexpected turbulence encounter. The purser will then contact the pilots with that information.
In the past, most of this would have been done via the interphone but the change to using these three specific PA announcements is part of the program to reduce FA turbulence injuries.