Docker uses Linux namespaces and control groups (Cgroups) to achieve container isolation. Namespaces provide isolation for processes, networks, file systems, users, etc.: PID namespace (process isolation), NET namespace (network isolation), MNT namespace (file system isolation), UTS namespace (hostname isolation), IPC namespace (inter-process communication isolation), USER namespace (user isolation). Cgroups are used for resource limiting and monitoring, allowing limits on CPU, memory, disk I/O, and other resource usage. These technologies ensure containers are isolated from each other while sharing the host kernel.