Abstract: A digital watermark is used to insert an imperceptible signal into data which may be in the form of images, audio or video. This has applications in a variety of purposes like copyright control, authenticity, captioning etc. As the watermarks are subjected to wide range of applications, each requiring different sets of properties, a variety of important characteristics and properties of watermarks have been investigated. This study highlights the important properties of watermarks and also gives insight into various trends and approaches prevalent in this area.The study also conducts a literature survey focusing only on noteworthy work and techniques used for images during preliminary and principal development stage of digital watermarking by various researchers with the utility of giving a fundamental understanding of the basic principles of digital watermarking as it has evolved. This may serve as the concrete foundation and the base for understanding further advances in this technology in later years.