The Substrate documentation uses a few typographical conventions that aim to maximize readability and provide clear cues for how to use example code and commands that you copy and paste from the manual.
Fixed-width text is meant to be typed or copied and pasted into a prompt or a file. Sometimes these may be fully formed commands that can be executed. Other times these may be fragments or starting points to be customized or expanded.
Words and phrases within fixed-width text that is surrounded by angle brackets are placeholders meant to show structure but not literal value. Sometimes the placeholder is a plausible, though not necessarily appropriate value as in -quality <default>. Other times the placeholder indicates the kind of value as in -assume-role-policy <filename>.
Italicized text elsewhere indicates a section or title on some other web page being referenced, as is commonly done when the Substrate documentation provides a walkthrough of an AWS, Azure, Google, or Okta interface as part of a larger task.
Quoted text is similarly used to indicate which check box or radio button to select on some other web page being referenced.
Bold text is used to indicate the text on a button you should click on.