https://support.microsoft.com/en-us/windows/common-file-name-extensions-in-windows-da4a4430-8e76-89c5-59f7-1cdbbc75cb01
.pkg and .dmg are files used to distribute and install applications on macOS. .pkg files are installer packages that may contain multiple files and executable code, while .dmg files are disk images that can contain a single bundled application or multiple applications. .app files are typically the main executable files for macOS applications. The other options listed are file extensions for applications or installers on other platforms (such as .deb for Debian-based Linux systems, .msi for Windows, and .apk for Android). This information is covered in the Comptia A+ Core2 documents/guide under the Mac OS section.