The main difference between daily fantasy sports and season-long fantasy sports is that daily fantasy only requires that fantasy owners generally select players for a specific day (or week with regards to the NFL).
Player selection in daily fantasy is typically done with a salary cap in place of the usual snake draft. In this format, players do not care about long-term sleepers and pay little regard to bad situations, and instead place emphasis on finding the highest amount of production at the lowest cost and creating the most complete squad.