A concept slightly more high level than a pointer. It's pretty much a pointer, but its memory address cannot be changed, and it does not need to be dereferenced, i.e. it is accessed as if it were a normal variable.

In C++ and similar languages, a reference is declared with the syntax type &name.

ex: void somefunc( int &ref_arg );, or
    int foo;
    int &ref = foo;