This strategy calls for looking at each asset, such as a stock or bond, based on its percentage change in value (or "total return") over a specific time period. This total return includes income the asset generates, such as dividends and interest, and increases in value, such as a rising stock price.
Essentially, you'd choose investments that could create cash flow from interest and dividends or capital gains (profits from selling them). Your payouts could come from any of these sources. If you don't feel comfortable selling assets, though, you may feel safer using a strategy focused on interest and dividend income instead.