A release is a planning and delivery cycle in agile software development that is used to operationalize a product roadmap and/or product portfolio.  It provides a high level view of the delivery schedule, often using themes or epics.  A release takes into consideration business and customer priorities, goals, dependencies, risks and other planning considerations in establishing release milestones.  Agile releases are generally shorter than traditional software development delivery cycles; typical agile development releases range from 3-6 months.  One goal of agile is to get software into the hands of customers or users sooner rather than later, to facilitate feedback and future prioritization.  On both ends of the release time-frame spectrum, there continue to be examples of multi-year projects, and under the right conditions, releases lasting less than a week.