A Target Date Fund is a type of mutual fund, where a team of experts provide an allocation to maximize an investor's returns by a specific date. This specific date is the “target date”, which typically corresponds to the year you turn age 65. The asset allocation of a target date fund starts aggressive (using stocks) and slowly becomes more conservative (using more bonds) as it approaches that target date.
The target date fund periodically rebalances its allocation to optimize risk by gradually shifting from an aggressive portfolio to a more conservative profile so as to minimize risk when the target date approaches. Target Date funds offer a diversified portfolio that is managed by experts, and it can be a good solution for an investor who does not want to manage it themselves.
Here is an example of a Target Date Fund Glide Path, which shows the allocation shift from stocks to bonds over the investment time horizon: