It is ultimately the gene product, or mRNA, that dictates which strand of one segment of dsDNA we call sense or antisense.
Most eukaryotic RNA transcripts undergo additional editing prior to being translated for protein synthesis.
Strictly speaking, only the mRNA makes "sense" with the genetic code, as the translated protein peptide sequence can be directly inferred from this strand.
Knowing the difference between the sense and antisense strands is important in certain molecular biology applications.
Identifying the different strands is also important in understanding small interfering RNAs, or siRNA.