File compression is the process of reducing the size of a file without losing any of its information. This can be done using a variety of methods, including lossless compression, which preserves all of the original data, and lossy compression, which removes some of the data in order to achieve a smaller file size.
There are many reasons why you might want to compress a file. For example, you might want to save space on your hard drive, make it easier to send a file via email, or reduce the amount of time it takes to download a file.