Generic Feature Format (GFF)
GFF is a standard file format for storing standardized genomic feature information. The files are stored in plain text format and are composed of 9 independent columns in standard tab-delimited format. GFF has several versions; the most recent is called GFF3.
More information about GFF3 and historic versions can be found here: http://gmod.org/wiki/GFF
The official and extremely detailed description of GFF3 can be found here: http://www.sequenceontology.org/resources/gff3.html
For reference, here is the standard definition for the 9 columns:
Column 1: Sequence ID (SeqID)
Column 2: Source
Column 3: Type
Column 4: Start
Column 5: End
Column 6: Score
Column 7: Strand
Column 8: Phase
Column 9: Attributes
There are numerous modifications and features that can be expanded on using the GFF format (e.g. nested features, quantitative data, sequence data). For a more thorough description of these advanced features see: http://gmod.org/wiki/GFF.