A qualified widow or widower status is for people who have recently lost a spouse and are at home supporting a child.
If your spouse died in the tax year and you could have used the tax filing status “married filing jointly” before his or her death (even if you didn’t actually file jointly), then, if you have a dependent child you can use the qualified widow or widower status for the next two years. For example, if your spouse died in 2017 and you haven’t remarried, you can file in 2017 jointly and then file in 2018 and 2019 as a qualified widow or widower.
Children are key. If the children are already out of the house when your spouse dies, this status will probably not work for you, because you have to have a dependent child or stepchild (except for a foster child) living with you. You must also provide for half the household expenses during the tax year. If the only reasons you cannot claim your child as a dependent because the child earned more than $4,200 in 2019 or filed a joint tax return, you can still qualify for this filing status.
The qualified widow or widower status affords you to file as if you were married. That gives you a much higher standard deduction and a better situation with tax brackets than if you filed as a single.