Living standard refers to the amount of money you have to spend (live on) after paying taxes, housing, Medicare Part B, contributions to retirement, and any other special expenditures you specify in the program. In other words, it's the amount left over to live on after you pay off-the-top expenses. Every other financial planning software that we know of asks you to specify your living standard (although they may call in "income needed" or some other term) and then they calculate everything based on your best guess. ESPlanner has patented software that calculates this "living standard" amount for you and makes sure it's the same amount in today's dollars for each year of your life.
Living standard is similar to discretionary spending except that it typically refers to "per-adult" spending amount instead of household spending amount. Per-adult living standard appears in the far right column of the Annual Recommendations report. Discretionary spending appears in the far left column of that same report. See also: Consumption Smoothing.