Sub-text?

[FlawlessHappiness]

There are also 2 other kinds which are Sign and Examine areas.

Both are a type of area you place and in the area you then refer to an entry you have to write in the .lang file.

Sign areas are areas that show a string of text when you're close enough and look at it.
Examine areas are areas that, when looking at it, changes the player's cursor, and when clicking on it, displays a string of text.

These are not specifically what you asked about, but I'd say they're in the same category.