A software-defined wide area network (SD-WAN) is a network that is abstracted from its hardware, creating a virtualized network overlay. It is an application of software-defined networking (SDN). SD-WAN is an automated, programmable wide-area network that dynamically and securely routes traffic based on applications policies, network conditions, or WAN circuit priority. Through a centralized interface, a cloud-delivered SD-WAN architecture allows companies to scale cloud-based applications across thousands of endpoints in the branch, campus, or SaaS and public cloud applications at distance.
reference: What is SD-WAN (Software-Defined Wide-Area Network)? (sdxcentral.com)