They contain religious inscriptions that memorialize the acts and rites of the Atiedian Brethren, a group of 12 priests of Jupiter with important municipal functions at Iguvium. They are written in the Umbrian language, one of the Italic languages related more or less closely to Latin. They shed light on the grammar of this ancient dead language, and also on the religious practices of classical paganism. They appear to be written in an accentual metre, similar to the Saturnian metre that is encountered in the earliest Latin poetry.
Here is a sample of their language and content:
"Jupiter Grabovius, if in your sacrifice there has been any flaw, any defect, any ritual violation, any fraud, any error, if in your sacrifice there is a flaw, either seen or unseen. . . "