Social networks are aimed at information sharing and friend-making due to the rapid development of Online Social Networks (OSN) and the increasing number of online users. The OSNs are also becoming an ideal platform for merchandise recommendation, opinion expression, information diffusion, and influence generation. Different types of social network services and users select the appropriate social network technology, services, and apps to meet their needs for sociability, entertainment, or information retrieval. User behavior involves user interaction, access, and browsing of the OSN. The users have different roles in different groups of social networks. Different identifications of the user may cause the user's intention to change. The user's intention may change as a result of different identifications. In this work, we discuss an introduction to OSN, single and multi-platform user behavior with various prediction models and recommendations".