Apple’s desktop and mobile operating systems provide a full suite of applications that allow you to do most of what you want without downloading any additional apps. You can browse the web, send and receive email, manage calendars and contacts, and much more, all with the stock apps included in macOS and iOS.
But on macOS, you have the choice to not use those apps. Say you want to use Microsoft Outlook instead of Apple Mail; you can make this change, and when you click a link to send an email, Outlook will open. Or if you want to use Chrome instead of Safari, the same thing will happen: URLs you click will open in Google’s browser.
In macOS Sierra, change the default web browser in the General pane of System Preferences. To change the default email client, go to Mail’s General preferences.
You can even change the default app to open any specific file type on the Mac. Say you work with plain text files, but have a text editor you prefer over Apple’s TextEdit. You can change this so every time you double-click a .txt file, it opens with your selected app. To do this, select a file, press Command-I, then expand the Open With section if it’s not already expanded. Click the popup menu and select the app you want to use, then click Change All.
But iOS offers no such option.
Read the rest of the article on Macworld.