Generally, lossy data conversion refers to the conversion of data from one storage format to another in a way that doesn't allow the exact recovery of the original data.
In particular, it can refer to lossy type conversion, where some values in the original type cannot be represented in the target type,[1] or to lossy file conversion, where the target format does not support all the feature of the original format.
Such conversions are typically used between incompatible software or as the export target of edition tools.
Most of the time, the document saved in the lossy format will look identical, but the conversion can also cause some loss in fidelity or functionality.
Such conversions are usually described separately as either lossy data compression or lossless data compression.