Jenkins is a CI tool, whereas Ant and Maven are build tools. Jenkins provides a trigger for the build to be executed. Maven and Ant can only perform build operations; however, Jenkins can run unit tests, deploy applications automatically.
Between Ant and Maven, Ant is just a tool and is procedural, whereas Maven is a complete declarative framework and has a lifecycle. Ant scripts cannot be reused, but Maven plugins can be reused. Ant is an old tool used by legacy systems. Most new applications use Maven.
