Back to back would be if you had to meetings coming up in chicago one on Jan 9 and then another on the next week on the 16th, and if you lived in say LA, to buy two tickets going the 9th-10th and then another one the 16th-17th would be vary expensive. Though if you bought a LAX-ORD ticket for the 9th-17th and then another one ORD-LAX 10th-16th, it would be a lot less because you would have a Sat. night stay for both tickets.