Software-Defined Networking (SDN) is the most advanced technique of the recent era. It provides reliability, flexibility, and logical centralization in terms of network control. SDN can adapt according to the operating environment. It has a centralized and cost-effective architecture capable of providing good network visibility. This not only increases resource utilization but also boosts performance. The pervasive existence and increase in intelligent programmable devices have given birth to SDN security, energy, efficiency, and network visualization. SDN has successfully countered security threats and attacks. A survey has been included that defines different strategies implemented during the process. We discuss the main ongoing research efforts, challenges, and research trends in this specific field to forecast the future evolution of this new paradigm. To summarise, readers can delve deeper and better understand the SDN structure, architecture, security threats, and countermeasures.