Answer
An unnamed namespace gives its contents internal linkage—they're visible only within the current translation unit, like static at file scope but working for types too. It's the modern C++ way to make helper functions, constants, or types local to a .cpp file, avoiding linker collisions with same-named symbols elsewhere.
namespace {
int helper() { return 42; } // internal linkage
}Real-world example File-local helpers go in an anonymous namespace so they don't clash with helpers in other files.