A "statement" (or "proposition") must, by definition, have truth value; i.e., it must be either true or false.
The second defining characteristic further restricts the class delimited by the first characteristic. Not all meaningful sentences express "statements." Some "sentences" express commands, questions, or exclamations. Only those sentences which have a meaning which can be said to be "true" or "false" are those which express "statements."

(Note that having truth value is identified with being either true or false, not with human knowledge of truth or falsity. There may be many statements known to be true or false; there are certainly many others whose truth value is unknown. For statements there are only two possibilities: T or F, but for human knowledge there may be three: T, F, or Unknown. The "truth value" of a statement is a "metaphysical" matter, or in other words it depends on the way the world is; it is a function of reality. Whether or not we (or anyone) knows the truth value of a statement is an "epistemological" matter; or in other words it depends on the evidence available to particular persons at particular times; it is a function of our beliefs about the world rather than the world itself.)
 

 
Truth Value: the property of a statement of being either true or false. All statements (by definition of "statements") have truth value; we are often interested in determining truth value, in other words in determining whether a statement is true or false. Statements all have truth value, whether or not any one actually knows what that truth value is. [A sentence which cannot be said to be true or false is without truth value, and therefore does not assert a "statement."  Questions and commands, for example are genuine sentences, but do not assert statements and thus have no truth value.]