The "Safe Withdrawal Rate" (SWR) is a financial guideline that helps retirees determine how much money they can withdraw from their retirement savings each year without running out of funds. A common rule of thumb is the 4% rule, which suggests that withdrawing 4% of your initial retirement portfolio annually, adjusted for inflation, can sustain your savings for about 30 years. This concept is based on historical market performance and aims to balance the need for income with the risk of depleting assets. Factors like investment returns, inflation, and individual spending needs can influence the appropriate SWR for each person, making it essential to tailor the approach to one's specific situation.