What's the difference between a 'to' and a 'through' target-date fund glide path?

This distinction affects how your risk changes around retirement. A to-retirement glide path reaches its most conservative allocation at the target date and then stops shifting, assuming you'll move the money elsewhere when you retire. A through-retirement glide path keeps reducing stock exposure for years or decades after the target date, staying more aggressive at retirement on the theory that you need growth to last through a long retirement. Two funds with the same target year can therefore hold very different stock percentages the day you retire, which matters a lot for sequence-of-returns risk. Before relying on a target-date fund, read whether it's a to or through design and check its stock allocation at and after the target date. Neither is universally better, but you should know which one you own.