A Coq developer works with the Coq proof assistant, a formal proof management system. Their role involves writing specifications, defining algorithms, and proving theorems about these algorithms. They ensure the correctness of software, mathematics, or protocols by formalizing them in Coq and verifying them against their specifications. This involves a lot of abstract thinking and problem-solving skills. They also contribute to the development and improvement of the Coq system itself, which involves programming in OCaml. They work in areas like software development, academia, or any field requiring high assurance software.