Typically, that refers to taking distributions based upon life expectancy. For example, assume that you are 40 years old, and the life expectancy tables show that a 40 year old male can currently expect to live to the age of 84 (i.e. 44 more years). You can begin taking penalty-free distributions now, if you take out 1/44th of your account this year and repeat the same process each year in subsequent years. Note that the percentage that you take out will increase over time, as your years of remaining expected life decreases (so, when 50 years old, you may have a life expectancy of 86 years, or 36 remaining years; so the distribution that year would be 1/36th of the account balance, etc).