The origin of Mobile ad hoc network (MANET) was started in 1970 as packet radio network (PRNET), later on different researches were made on it in different ages. MANET works under no fixed infrastructure in which every node works likes a router that stores and forwards packet to final destination. Due to its dynamic topology, MANET can be created anywhere, anytime. As there are limited resources in MANET so it faces many problems such as security, limited bandwidth, range and power constraints. Due to this, many new routing protocols are proposed. This article examines different techniques to manage congestion control, security issues, different layers attacks, routing protocols and challenges that are faced by MANET.