These days the usage of network is growing at a faster pace, at the same time a lot of challenges is facing by the net- work administrator, to tackle the frequent network access by the users. The network infrastructure is growing rapidly to meet the business need, but it requires re-policing and reconfiguration of the network. But managing the under- lying infrastructure becomes more complicated to handle the unprecedented network demand. The Software Defined Network (SDN), is the next generation Internet technology, which not only solves the ossification of the Internet, but also creates innovations and simplifies the network management. The key idea behind SDN is separation of control plane from the data plane, as a result, devices in the data plane simple becomes the forwarding device and transfer all the decision- making activities in a centralized system called a controller. Among many, OpenFlow is the standard and most popular SDN protocol that interacts between controller and forward- ing devices. In this article, we will give an overview of the basic architecture of SDN and OpenFlow, SDN-controller interaction and benefits of SDN.