Lazy portfolios are designed to perform well in most market conditions. Most contain a small number of low-cost funds that are easy to rebalance. They are "lazy" in that the investor can maintain the same asset allocation for an extended period of time, as they generally contain 30-40% bonds, suitable for most pre-retirement investors.
There are a number of popular authors and columnists who have suggested 3 fund lazy portfolios. These typically consist of three equal parts of bonds (total bond market or TIPS), total US market and total international market.