Italicized words are used for various purposes in text:

1. Emphasis: The text is being highlighted because of its significance.
2. Reference: Proper names of subjects are sometimes italicized to identify them and make them stand out.
3. Convention: In many forms of literature, italicized items are common usage. In old indexes, for example.
4. Scientific: Many scientific texts italicize the full scientific names of subjects.

(In context with types of text)