A power of attorney (POA) is a legal document that gives another person the authority to make decisions and take actions on your behalf.  Another option is a Limited POA which is only in effect for a specific period or for a specific purpose. 
A POA can be used for many things include managing finances, making healthcare decisions, managing real estate and other assets, and conducting business transactions. Lastly, be sure to choose someone you trust.  Have a conversation with them about what you expect of them before you grant POA designation.