Comment by Itaxpica

It means that your normal vest schedule doesn’t start for one year, so if your initial stock grant vests quarterly, none vests at all for the first year and then 25% vests all at once after year one, then the other 75% of it vests quarterly over the following three years. Essentially it’s a small, localized version of golden handcuffs for the rank-and-fils, since it means if you leave the company within the first year you get no stock.