Linked Styles

This was introduced in Word 2007.
Linked styles are a combination of paragraph styles and character styles.
Some styles can be applied to either characters or paragraphs depending on what is currently selected

If you select a paragraph or click inside a paragraph and apply a linked style, it is applied as a paragraph style

If you select a single word or phrase and apply a linked style it is applied as a character style.

Linked Styles
In Word 2003 all paragraph styles where linked styles
These allow you to create "run-in" headings where only the first few words (or characters) of a paragraph are formatted as the heading.
This meant that the style could either be used on a full paragraph (as a traditional paragraph style) or on just a range (as a character style) and both would appear at the same level in the TOC.
Word 2007 introduced "Disable Linked Style" option on the Styles task pane.

You cant associate a start at value with a paragraph style because it is better to have all the paragraphs within a given list level share the same paragraph style.

Style Task Pane

Paragraph styles are indicated with a paragraph symbol 'P'
Character styles are indicated with a character symbol 'a'

Linked styles are indicated with both a 'P' and an 'a'
Linked styles are indicated with both a 'P' and an 'a'

Built-in Linked Styles

Heading 1
Heading 2