macOS Catalina (available late 2019) dropped support for 32bit apps. macOS Mojave had been warning us about this every time we launched one of these apps, and action on your part is now needed if you upgrade beyond macOS Mojave. One of the most popular 32bit apps we see is Microsoft Office 2011, which includes Word, Excel and PowerPoint. If you have been limping along with Office 2008, the same warning applies. See the icons below to determine which version you have.
If you are planning on upgrading to Catalina, Big Sur or Monterey, you may want to purchase a new version of Office. The Office 2021 version began shipping on Oct 5th of 2021. The “perpetual” version is $149 (for Word, Excel and PowerPoint) and Office 365 starts at $69 a year.