How is DevOps related to Agile?
DevOps and agile aren't same thing but they are complimentary to each other. Agile development is development that adheres to the principles stated in The Agile Manifesto. In brief, agile is the word for an environment in which the priorities, according to the authors of the manifesto, are-


Individuals and interactions over processes and tools
Working software over comprehensive documentation
Customer collaboration over contract negotiation and
Responding to change over following a plan.


The point of DevOps is to deliver technology to business units in a timely fashion and ensure the technology runs without interruption or disruption. To achieve it's goal DevOps mostly focus on-


deep communication between software development and IT operational groups 
automated deployment processes


Below are list of relation/differences with agile and DevOps-


Agile software development is a methodology for developing software, but DevOps, on the other hand, is all about taking software which is ready for release and deploying it in the safest, most reliable manner possible.
Agile is all about development. Sometimes, it takes over the entire company. Even when it does, agile discipline doesn't inevitably lead to DevOps. The practice of DevOps involves a separate discipline and methodology from those of agile.
Agile practices, like Continuous Delivery practices, can be part of a DevOps activities.