The Default Dock on macOS shows off many of the apps that come bundled with your Mac out of the box. Many users customize it right away by adding apps they use on a regular basis, and removing those they don’t. However, some people may prefer to have a cleaner Dock, and to minimize the apps that show up on the Dock. One way to do this is to make the Mac Dock only show apps that are currently running.
Apart from the stock apps, the Dock also shows the apps you’ve manually added, the apps you’ve launched, and lastly, the Downloads folder, and the Trash where you move all your unwanted files. If you have a lot of apps stored on your Dock, you may sometimes have trouble figuring out which apps are currently open and running on the system, even with the little app running indicator at the bottom. If you’d prefer, you can set the Dock to display just the active apps and remove all the rest, by using a defaults write command.