Wireless sensor actor network (WSAN) adverts to the combination of mainly one coordinator node with two types of network nodes: sensors and actor nodes that communicate wirelessly to perform allotted sensing, monitoring and actuation chores. To provide effective and reliable WSAN performance, the coordinator node of a WSAN must be able to administrate the network, sensing nodes and synchronize the actor actions with appropriate commands order based on data gathered momently by sensing tasks. The latest advances in technologies have led to advances in monitoring the environment, collecting data, processing the sensed data, threshold-decision making process and lastly performing of suitable actions. This batch of processes could be carried out with distributed wireless sensor network and actor network, which yields a wireless sensor actor network (WSAN). This paper explores WSAN definition, uniqueness and the main design concepts and applications. A detail comparison of WSAN and ad hoc network also presented.