A reference is a value that enables a program to indirectly access a particular datum, such as a variable or a record, in the computer's memory or in some other storage device.
A reference is a value that enables a program to indirectly access a particular datum, such as a variable or a record, in the computer's memory or in some other storage device. The reference is said to refer to the datum.
In some programming languages, copying a variable may be implemented as either a copy by value or a copy by reference. When it is copied by reference, a reference to the data will be assigned, and the underlying data is not copied. Often, object datatypes will be copied by reference by default (for example, in Java), while primitives will be copied by value.
A nice article on pass by reference
