DevOps is a culture in an organization, where the development team and operations team help each other by sharing information, process and tools to successfully develop and maintain a software application.
Software development and software testing are not separate in DevOps world, Dev includes software development and it's testing.
Ops (Operations) team is responsible for software deployment and it's maintenance in the production or live environment, with no or limited communication with the dev team.
DevOps bridges the gap between the Dev and Ops team for successful software development and deployment.