Ipe drawings are stored in ipe or mipe format. ipe format is used for single figures, and can be included into your LaTeX files or treated as an Encapsulated Postscript file. The mipe format does not contain Postscript information and can only be read back by Ipe itself. It is used for multi-page documents.
Besides the LaTeX and Postscript information, the files contain a description of the drawing in a (keyword, parameter) format. This format is documented.