Could be...

Specially in oppsition to the other kinds of texts listed

:-

I think what is really meant is 'brödtext' as surely there can be facts in the footnotes and the image texts.

They probably mean the main, general text (of the relevant sort of publication), in distinction from the captions and footnotes which also may occur in the same publication.
In general, you would refer to this sort of text as the "main text", the "body text" or the "general text".

The "fakta-" part indicates that it is text of a nature distinct from fiction and generally informative in nature (i.e. expressing facts, using data, etc.).

"a piece of writing that conveys information, such as data or knowledge of any kind"
http://answers.yahoo.com/question/index?qid=20080313230706AA...

:o)

This is just another alternative to Diarmuid's suggestion of "text box". I think that if the context is traditional printed publications such as newspapers or books, then the more general term "information box" to describe a box inserted into the main body of the text to provide background information may be more appropriate.

This glossary treats "faktaruta" and "faktatext" as equivalents (and also gives definitions of "bildtext" and "brödtext"):
Faktaruta, faktatext – ingår ibland i en större artikel för att ge bakgrundsinformation.
http://sjuannollnio.skolbloggen.se/files/2009/11/Tidningskun...

However, if the context is word processing and DTP, then the more specialised term "text box" seems more appropriate, e.g.:
References: Captions, Text Boxes, Footnotes and Endnotes
http://classes.bus.oregonstate.edu/winter-06/ba131/Activitie... Captions, Text Boxes, Footnotes and Endnotes