Investing in a target-date fund is a great way to save for retirement. A target-date fund is a type of mutual fund that automatically adjusts its asset allocation based on the investor's retirement date. The fund will become more conservative as the investor gets closer to their retirement date.
From Wikipedia
A target date fund (TDF), also known as a lifecycle fund, dynamic-risk fund, or age-based fund, is a collective investment scheme, often a mutual fund or a collective trust fund, designed to provide a simple investment solution through a portfolio whose asset allocation mix becomes more conservative as the target date approaches.