A default browser is the web browser that your computer or device automatically uses to open web pages and links. When you click on a link in an email or a document, your default browser will open to display the webpage. Most operating systems, like Windows, macOS, and mobile OS, allow you to set a default browser of your choice.
For example, if you set Google Chrome as your default browser, any link you click will open in Chrome. If you prefer another browser like Firefox or Safari, you can change the default settings to use that browser instead.
Setting a default browser is useful because it ensures that all web links open in the browser you are most comfortable using, without having to manually select a browser each time.