Software-Defined Wide Area Network (SD-WAN) is a type of networking technology that is used to improve the performance and flexibility of wide area networks (WANs). It is designed to simplify the management and operation of WANs, and can be used to connect branch offices, data centers, and other locations over long distances. 

SD-WAN solutions typically involve the use of software-defined networking (SDN) technologies to abstract the network layer from the underlying hardware, and to allow the network to be centrally managed and controlled. This can allow organizations to provision and manage their WANs, and scale and adapt to changing business needs more easily. 

SD-WAN solutions can be used to improve the performance and reliability of WANs by using multiple links and optimizing traffic across them. They can also be used to reduce costs by allowing organizations to use lower-cost links, such as the Internet, for some types of traffic.