When you have a title of something what do to it underline or italic?

You generally italicize titles of longer works, like books, movies, albums, and plays.

You underline or put in quotation marks titles of shorter works, such as articles, poems, songs, and chapters.

Here's a breakdown:

Italicize:

* Books: *Pride and Prejudice*, *The Great Gatsby*

* Movies: *The Lord of the Rings: The Fellowship of the Ring*, *Titanic*

* Albums: *Abbey Road*, *Thriller*

* Plays: *Hamlet*, *A Streetcar Named Desire*

* TV Shows: *Friends*, *Game of Thrones*

* Journals: *Nature*, *The New England Journal of Medicine*

Underline or use quotation marks:

* Articles: "The Future of Artificial Intelligence"

* Poems: "The Road Not Taken"

* Songs: "Bohemian Rhapsody"

* Chapters: "The Battle of Helm's Deep"

* Short Stories: "The Gift of the Magi"

* Essays: "Self-Reliance"

Note: Some style guides may have slightly different conventions. If you are unsure, always check the specific style guide you are using.