Apple announced last year that they are beginning to phase out support for 32-bit applications for macOS. Beginning in January 2018, the Mac app store will no longer accept any 32-bit apps. Starting with macOS High Sierra 10.13.4, Apple will begin warning users about installed applications that are 32-bit, but will continue to run them without problems.
Apple has not yet announced the release date of macOS 10.14, or when Mac users will no longer be able to run 32-bit applications.
It is recommended that all users review their current software, and begin working with vendors to determine whether 64-bit support will be added, and whether you should budget now for an upgrade.
To check if an application is 32-bit or 64-bit do the following:
Type “Command ⌘ + Space bar”, or click the magnifying glass in the menu bar, to launch Spotlight
Type in System Information and hit Enter when it shows up
Scroll down to the Software section in System Information
Click Applications and wait for your applications to load
The column to the far right in the Applications table will give you a simple, "Yes" or "No" answer as to whether or not your app is 64-bit
As for Windows users, Microsoft has not announced any plans to deprecate 32-bit support for Windows, but users should begin to review Windows applications also.