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Tuples group a fixed number of values. Written with {}:

Point = {3, 4},
{X, Y} = Point,                 % pattern match — X=3, Y=4
Person = {person, "Ada", 36},   % tagged tuple — convention

Tagged tuples are an Erlang convention: the first element is an atom describing the tuple's purpose. The Erlang ecosystem uses this everywhere:

{ok, Value}     % success
{error, Reason} % failure

Functions return tagged tuples instead of throwing:

case file:read_file("data.txt") of
    {ok, Contents} -> use_data(Contents);
    {error, Reason} -> log_error(Reason)
end.

case is Erlang's pattern-match expression. It's like a switch that destructures.

case X of
    0 -> zero;
    N when N > 0 -> positive;
    _ -> negative
end

Clauses end with ;, the whole case ends with end.