Google has announced that, beginning in January, ad groups in Google video and display campaigns that do not have any targeting set at that level will automatically be eligible to show ads on the Google Display Network.
Google has been sending advertisers a notice and pausing display and video campaigns that didn’t have targeting assigned to ad groups so that ads didn’t run without any targeting. As of January, that will no longer happen. After the change, if you have one or more ad groups without targeting in a video or display campaign, those ads will be eligible to run generally across the Google Display Network.
In other words, your ads will run without any targeting limitations at all apart from whatever location, device and language setting have been applied at the campaign level. If you don’t want your ads to run without additional targeting at the ad group level, you should pause the ad group or add targeting.