With the advent of macOS 10.15 Catalina (expected to release sometime in early fall 2019), Apple will be removing support for all 32-bit applications. Apple has been warning about this for a few years now and has gotten increasingly aggressive at informing users who run macOS 10.14 Mojave that they have dated applications that won't work in the future.
This blog entry will detail one person's efforts to clean his system of 32-bit applications (or at least become aware of the applications that will be an issue).