Darts on purchased patterns come in a variety of sizes and shapes. They take in fabric to add shape to the garment. Dart placement is a fitting issue and may require alterations. Find more information about alterations here.
Darts can have one or two pointed ends. Some darts have curves. Transfer the markings that are on the pattern piece on to your fabric, using dressmakers carbon. (Learn more about marking fabric). The center marking may not be included on the pattern marking. If it is, it is simply the fold line.