MANET is a special kind of wireless network. It is a collection of mobile nodes without having aid of established infrastructure. Mobile Adhoc network removes the dependence on a fixed network infrastructure by treating every available mobile node as an intermediate switch, thereby extending the range of mobile nodes well beyond that of their base transceivers. Other advantages of Manet include easy installation and upgrade, low cost and maintenance, more flexibility, and the ability to employ new and efficient routing protocols for wireless communication. In this paper we present four routing algorithm, classifications, discuss their advantages and disadvantages.