A Gherkin developer uses Gherkin language to write and manage test cases for software development. Gherkin is a plain English text language that allows the developer to describe software's behaviour without detailing how that behaviour is implemented. It's widely used in Behaviour-Driven Development (BDD) for writing acceptance tests. The Gherkin developer's role includes defining features and scenarios, writing step definitions, and ensuring the software behaves as expected. They collaborate with stakeholders to understand the software requirements, translate these into Gherkin syntax, and work with the development team to ensure the code meets the defined criteria.