This document summarizes a survey paper on wireless sensor networks. It begins by defining a wireless sensor network as a collection of spatially distributed autonomous sensors that cooperatively monitor physical conditions like temperature, pressure, and pass data to a centralized point. The key components of a sensor node are then described as a sensing unit, processing unit, transceiver, and power source. Different types of wireless sensor networks are outlined, including terrestrial, underground, underwater, multimedia, and mobile networks. Characteristics and applications of wireless sensor networks in fields like military, environment, health, home automation, and commerce are also summarized.