This refers to the practice of automatically, systemically, setting aside a pre designated amount of money into your savings account immediately upon getting paid before using your paycheck for anything else.
Typically, the intent is to realize that your biggest and most important debtor isn’t any of them you think it is but rather: future 70yo you needing financial support that current 30yo you owes to yourself.
Your debtors are important. More important than your current yous *wants*. But they are not more important than your *today*needs nor the needs of your later years. You should buy the food you need today, and save for retirement for tomorrow, and only then pay your bills.