DNA carries information in the form of a sequence of nucleotide bases along one strand, matched by complementary bases along the other strand. This structure of DNA provides an efficient mechanism for accurately copying each molecule during replication. As a result, two identical copies of the parental DNA molecule appear. This promotes inheritance of the parental traits in the offspring.
Additionally, there are many possible combinations of units that make up a DNA molecule. This provides genetic diversity. At the same time, the structure of the sugar-phosphate backbone provides some stability so common sets of proteins can interact with all DNA molecules. This suits the job of carrying heritable information, which is, however, diverse to better facilitate evolution.