Question: "Phylogenetically informative" characters are those that can discriminate between at least two of the n possible trees by the criterion of parsimony. In practice, informative characters have states that are shared by at least two taxa. For example, a character that has the distribution of [A,B,C,D,E] among five taxa (that is, each of the five taxa have a different character state) is not phylogenetically informative (though for DNA this would only make sense with four taxa because there are a maximum of four different nucleic acids in DNA). Similarly, for two sets of five taxa [A,A,A,A,A] or [A,A,A,T,A], neither arrangement is phylogenetically informative. A character that has the distribution [A, A,T,T,C] among five taxa, however, is phylogenetically informative because at least two taxa have the same characters (two have A and two have T, in this example).
Additional comments: Can someone explain phylogenetic significance in different words? Would TAACA be significant because at least two taxa share A?