What difference between std.typecons.Tuple and std.meta.AliasSeq

[John Colvin via Digitalmars-d-learn]

On Sunday, 20 September 2015 at 18:28:13 UTC, Alex Parrill wrote:
> (though you can declare a variable using an AliasSeq containing 
> only types; I think this acts like defining one variable for 
> each type in the seq).

This is what is used inside std.typecons.Tuple