A Makefiles developer creates and manages Makefiles, which are special format files that help build and manage projects automatically. They write rules and targets that describe the project's dependencies and the commands needed to fulfill them. The developer uses Make, a build automation tool, to execute these Makefiles. This involves automating code compilation, linking, and generating executable files. Makefiles developers also troubleshoot issues related to build processes and dependencies, optimizing them for efficiency. Their skills are crucial in large software projects where manual compilation and linking of numerous files would be time-consuming and prone to human error.