Also, most types of data (for example text, image or sound) have many varieties of file formats, all with their own special strengths and weaknesses.
There are, for example, more than five ways to store text as a file. Two of the most known ways are: the plain .txt format and the simplest of the HTML formats. The difference is that a .txt file can only store a sequence of characters but an HTML file can also store links to other files and the formatting of the text, for example whether the text is bold, underlined or italic (but usually HTML should say whether the text is very important, a link, or not very important; whether important text should be bold, italic or red is then specified using a file in a special format called CSS).
There is often a choice between saving a file in a simpler versus a more complex file format. The simpler format will make a smaller file, but store less information. The more complex file format will usually be a larger file and more difficult to use, but can store more information; sometimes a faster computer might be needed in order to use a more complex file format.
File formats made for commercial proprietary software are sometimes a secret, so that people who do not work in the company which made the proprietary software cannot use their own and others' files in the format without buying their software. That action is called vendor lock-in, and can be used to make a monopoly. Because of that, it is sometimes a crime.