Tuple are an existing concept in Programming.
According to the Solidity Documentation:
A tuple is a list of objects of potentially different types whose number is a constant at compile-time
Tuples are not a proper types in Solidity. There is no tuple keyword is Solidity. Therefore, you can’t assign a tuple as a type to a variable.
However, the official documentation states that Solidity internally allows tuple types and can only be used to form syntactic group of expressions.
Tuples can be used to return multiple value at the same time. These can then either be assigned to newly declared variables or to pre-existing variables (or LValues in general)