As the name suggests, it involves little to no effort.
So much of our lives are spent trying, striving- working effort-fully towards a certain outcome.
AND many meditation practices have that quality as well - making conscious efforts to build concentration or clarity. This technique can serve as a counterbalance to that effort, a brief reprieve from all that trying so hard. It can be very liberating. It can also be very frustrating. See what comes up for you!