Transmitting confidential images between two channels suffer from hacking. Therefore, protecting confidentiality has become a very essential issue. Recently, several methods are developed to protect important information. The main idea is based on embedding important information in multimedia carrier such as: text, image, audio, and video. The developed methods may be classified as steganography and watermarking. Steganography aims to embed huge amount of secret data in multimedia carrier while watermarking aims to hid small amount of secret data in multimedia carrier. This paper first presents a literature survey of information hiding, then classifies the proposed methods, and finally introduces a comparative study between the different methods.