For compatibility with earlier 16-bit DOS and Windows 3.1 applications, Windows 95/98 created an 8.3 short name that was maintained alongside the long name. That compatibility was dropped in Windows ...

Short file names, all lower case, hyphens between words (e.g., illustration-curriculum.pdf). No spaces, periods, underscores, or special characters—only the file extension, such as .pdf or .jpg, ...