There are some apps on your Mac you cannot delete that are automatically installed by macOS, like Mail, Music, Books, Notes, Podcasts etc. The same apps you normally find on your iPhone or iPad that you also cannot delete. If you do want them to be gone, however, you an hide them or remove them from your dock, and that way they'll at least be out of sight.
Outside of that, some apps you'll download will come with their own 'uninstaller program' that you will also find in the app page. These will come with detailed instructions on how to install the app from your device.