Online services have made the various computer applications accessible and convenient for their users. In last one decade, the usage of sophisticated personal gadgets and Internet connectivity have increased manifolds, which in turn have drastically changed the way of doing the official as well as personal activities. These gadgets are very powerful and highly portable, which can serve multiple purposes like communication, entertainment, business and banking etc. It is necessary for any secure information system to provide its users certain security services like confidentiality, integrity, authenticity and availability. Authentication is a core component of every security model. As the security needs for accessing various types of online accounts are different and there exists different transmission technologies also, so a variety of authentication methods exists to provide the authentication services. Adoption of BYOD (Bring Your Own Device) trend and development of powerful portable devices have led to an increasingly heterogeneous authentication landscape. There exists no single technology that can meet these diverse authentication requirements. The authentication techniques used in the wired networks may not fit directly in wireless networks. In this paper we have studied, analyzed and presented various authentication methods, attacks, issues and technologies used in entity authentication deployed in WLANs. The scope of this paper is only limited to the authentication concerns in WLANs. As the broadcasting nature of wireless channel makes them drastically different from their wired counterparts, so the features and properties of protocols deployed in WLANs for providing the security services are different, and face a unique set of challenges.