What type of compression results in permanently removing some data to decrease file size?

Lossy compression is a method that achieves a reduction in file size by permanently eliminating some data. This typically involves removing elements that are less critical to the overall quality of the data, which is especially common in audio, video, and image files. For instance, in image compression, details that are not easily perceivable to the human eye may be discarded. As a result, while the file size decreases significantly, there may be a perceivable loss in quality, which is why it's billed as "lossy."

In contrast, lossless compression retains all original data and allows for the exact reconstruction of the original file. This is important in contexts where data integrity is critical, such as in text documents or executable files. Data compression is a broader term that encompasses both lossy and lossless methods, without specifically denoting the removal of data. File truncation involves cutting off parts of a file but does not pertain specifically to compression techniques. Therefore, lossy compression is specifically recognized for the intentional trade-off between file size and data quality.