A Linux Internals developer is involved in designing, implementing, and maintaining the Linux kernel, which is the core part of the Linux operating system. They work on various subsystems such as memory management, process management, file systems, device drivers, and networking. They also troubleshoot and fix bugs in the kernel and optimize its performance. Their work often requires deep understanding of computer architecture, data structures, and algorithms. They may additionally contribute to open-source projects, collaborate with other developers worldwide, and assist in the development and testing of new kernel versions.