In one year from now, Microsoft will end support for the Office 2013 suite of products. This comes after five years of mainstream support, and an additional five years of extended support (via Bleeping Computer.)
This move will specifically take effect on April 11, next year, in 2023. In return of this warning, users will have adequate time to make the necessary changes and transition to another product like Office 2019, Office 2021, or Microsoft 365 subscriptions. However, this does not mean that you will no longer be able to use these apps after the date. Rather, it just means you won't get security patches, which could put your device and organization at risk for viruses and other issues. You also won't get official technical support from Microsoft, either after April 11, 2023.
Remember, Microsoft has a full list of products ending support in 2023 over on this website. Along with Office 2013, some products include Windows 8.1, Visual Studio 2012, Windows RT, Internet Explorer 7, and more. Though not official, there's also a comprehensive list of its dead Microsoft products online, too.