Previously, we consider that the state of a sensor covering targets is in binary mode: success (cover the targets) or fail (cannot cover the targets). However in the real world, a sensor covers targets with a certain probability, called the Probabilistic coverage, due to various issues which cause the uncertainty and form various probabilistic models, including the probabilistic network model, the probabilistic sensing model, the random noise model, the random fault model, etc. About probabilistic coverage, there is a quite long survey. Here, we introduce this subject briefly. The reader may refer the survey if would like to study more.