Investment for income refers to a situation where you need to regularly withdraw a part of your investment to meet your living expenses. Generally this is done by retired people or others who don't have a real income.
When an investment is made for income rather than for accumulation, many of its key features need to be different than if you were investing just to grow your wealth. First and foremost, it needs to be predictable. When money is accumulating for use much later, then it doesn't really matter if you get somewhat higher or lower returns at different times. It doesn't even matter if you lose money for some of the time as long as gains made over time more than balance it out. However, when you need to make regular withdrawals, then this unevenness is not desirable.
