Short range usaully means reading barcodes while almost touching the barcode with the end of the reader, or a few inches away.

Long range can mean reading the barcode from distances of; 7", 14", 21" or even over 30". Typically these longer ranges are only for linear barcodes, as 2D barcodes are trickier to read at distance; typically the range is up to around 9".

Long range is useful - it makes people's jobs easier - when reading barcodes for example, on the second shelf (epecially if the user is not 7' 5" tall). Also help reading barcodes in awkward positions, like leaning through a forklift truck window, or reaching in to a pile of boxes.