The term "format" has several meanings, related to 1) disk formatting, 2) page formatting, and 3) file formats.
1) Disk formatting
In order for storage media, such as a hard drive or flash drive to be recognized by your computer, it first needs to be initialized, or "formatted." Formatting a disk involves testing the disk and writing a new file system onto the disk. This enables the computer to read the disk's directory structure, which defines the way files and folders are organized on the disk.
You can use a disk utility program to format or reformat a disk. This will create a blank, empty disk for storing your files. Therefore, only format disks that don't contain important data or make sure you have backed up your data before reformatting a disk!
When you reformat a disk, it will appear to be empty. This is because the directory structure has been rewritten, making the entire disk space available for writing new data. However, the old files are still on the disk. They just don't show up since they are no longer included in the directory structure. So if you accidentally format a disk (which is pretty hard to do), you may be able to retrieve your files using a disk utility such as Norton Disk Doctor or DiskWarrior.
2) Page formatting
The term "format" can also be used to describe the page layout or style of text in a word processing document. When you format the layout of a page, you can modify the page size, page margins, and line spacing. When you format the text, you can choose the font and font size, as well as text styles, such as bold, underlined, and italics.
3) File formats
A file format refers to the way data is saved within a file. For example, some files are saved in a plain text format, while others are saved as binary files. Software developers often create proprietary file formats for their programs, which prevents the files from being used by other applications.