They are mostly equities and riskier investments early on, then auto-adjust to lower risk dividend stocks and treasuries when you are closer to the target fund date to support pulling out money every month to live on.
They also tend to have higher fees and a smaller return than managing it yourself with index funds and bonds. But for people that don't want to do that it is a good option none the less.
Just plow your 401(k) into Fidelity Freedom Fund 2055 (or whenever your retirement year is - they have many options) and forget about it.
https://www.fidelity.com/mutual-funds/fidelity-fund-portfoli...
They are mostly equities and riskier investments early on, then auto-adjust to lower risk dividend stocks and treasuries when you are closer to the target fund date to support pulling out money every month to live on.