A Power Of Attorney is someone you appoint to make legal and financial decisions on your behalf in case you are no longer able to do so.
If you should become incapacitated and a Power Of Attorney has been appointed, there won't be a lapse in your ability to control your finances or legal matters, as the agent will be able to act on your behalf. If you become incapacitated without a Power Of Attorney, no one can legally handle your financial affairs.
In order to name one, you're going to need to work with a lawyer or an online legal service. This worksheet can prepare you for the conversations and decisions you’re going to have to make.