dropped vs detected

Hi Folks, We have a pair of FG 240D' s sitting behind our ASA. These were config' d by a vendor so they are a black box to us, looking for what should be to the forum some simple answers. The vendor setup an outside VDOM with DoS policies. For most attacks, we are seeing a status of dropped which I' m told means blocked. For anomalies, we get a status of detected, which is making management question the configuration. What is the difference between dropped and detected? Is " detected" a problem that is not dealt with? Many thanks in advance. buddyd