Agree with @Thedannymullen in that the Insteon App is about the worst thing I’ve ever seen in IOT and there is a lot of crap out there. Once you get up and running with OH, you’ll never want to open that app.
From a technical perspective what happens is this, you command the Hub to send a command and turn on a light via the app. The light turns on but OH has no way to know this happened. Later (could be minutes) OH polls and find the light on and updates itself. This isn’t a huge deal most of the time, but if you have an OH rule written to do something when that light turns on, the rule will then trigger much later. I’ve had it happen where polls get missed and rules trigger like an hour later. It can be very difficult to figure out in the beginning and makes it seem like there are “ghosts in the system”.