Typically, the word slides refers to mounted 35mm positive transparencies. Often, it used to mean a positive transparency of any size or format and is used to distinguish positive films from negative films. Ilfochrome Classic is a positive print material, i.e., it will reproduce what is projected onto it. If you project a color negative, the print will not look like the original scene, but will have a strong orange tinge and its colors reversed, just like the negative itself does.