A FreeBSD developer designs, develops, and updates the FreeBSD operating system, an open-source Unix-like OS. They write and debug code, typically in C, and contribute to various system components such as the kernel, device drivers, or userland programs. They also work on maintaining system security and stability. Additionally, they collaborate with other developers globally, review code changes, and participate in testing and debugging. Their role also involves documenting changes, responding to bug reports, and providing support to users. They may specialize in areas like networking, file systems, or virtualization within the FreeBSD project.