What is tuple and when to use

A tuple is a data structure that has a specific number and sequence of elements. It allow us to combine multiple values with similar or different types into single object without creating a custom class. It can also be used where we have to return multiple items from the method instead of “out” keyword.
From MSDN:

Tuples are commonly used in four ways:

• To represent a single set of data. For example, a tuple can represent a database record, and its components can represent individual fields of the record.
• To provide easy access to, and manipulation of, a data set.
• To return multiple values from a method without using out parameters (in C#) or ByRef parameters (in Visual Basic).
• To pass multiple values to a method through a single parameter. For example, the Thread.Start(Object) method has a single parameter that lets you supply one value to the method that the thread executes at startup time. If you supply a Tuple<T1, T2, T3> object as the method argument, you can supply the thread’s startup routine with three items of data.