RLE

RLE usually stands for run-length encoding:
 * Run-length encoding

Formats known as "RLE" include:
 * Utah RLE
 * CompuServe RLE

See also:
 * Run-length encoding
 * Category:File formats with extension .rle

Note that there are many other formats, not listed here, that use run-length encoding. "RLE" often has a domain-specific meaning, e.g. as a compressed subtype of some format.