The dumbbell pullover is an interesting exercise because some say it is good for the chest while others say it is good for the back (lats).
I tend to use it more for the lats especially when someone doesn’t have access to a pull-up bar or lat pulldown machine, but hell since it works the chest you can throw it in for that too.
The key to this is not extending your elbows like a skull crusher during the exercise. Get a good stretch at the bottom when letting the dumbbell go behind your head.
Set it up by putting your upper back on a bench and hold the dumbbell with your palms up just like a skull crusher. This is also good for getting some mobility in your upper back and also shoulders.
See this video