Brackets

Indicates a mouse click with the name of the command in the brackets.

click [Apply] or click [Update]

Italic

Indicates placeholders, most often used to describe filling out a sequence of  parameters in a form; these placeholders represent information that must be supplied by the user.

My name is yourname.

You would type the following

My name John Smith.
 

Quotes

Items within quotes are taken literally

"John Smith"

You would type the following:

 John Smith

Plus sign

Indicates a combination of keys. For example, ALT+F1 means to hold down the ALT key while pressing the F1 key.

ALT+F1

Capital letters

Indicates the names of keys and key sequences.

ENTER

CTRL+R

Bold

Bolded text is used to indicate different areas of subject matter.

This documents title is:
Document Conventions

Parentheses

Text within parentheses further explains an item.

John Smith (voter)