The human genome is a book of 3 billion "DNA" letters (A, T G, and C) called nucleotides. Only about 1.5% of those letters get translated into proteins, the structural components of body tissues, enzymes and antibodies. That small portion of the DNA that codes for proteins is called the exome. It represents some of the most important and well-studied pieces of your DNA, but the other parts of your DNA are important, too!
Helix's sequencing technology is called Exome+ (Exome plus). The genetic experts at Helix have identified other important information-rich areas to sequence and the "+" represents that part.