"Data" in the field of computer science is a term that simply refers to information that is in an electronic form and that usually is stored in a database. "Dynamic" denotes change, and when the word is used to describe data — as in "dynamic data" — it refers to electronic information that changes as needed or desired. There are many reasons why data would need to be dynamic. For example, large electronic commerce web sites that offer many different products for sale almost always have to keep track of inventory. Product information is stored in a database and is retrieved and updated in real time.
If one visitor purchases the last of a product, a "sold out" notice might be programmed to display to subsequent visitors. The electronic information displayed would reflect the changes in the database that were made as a result of the purchasing activities of cyberspace customers. This is a prime example of dynamic data in the real world.
Most websites are database driven or simply data driven. This means that the content of such sites is created on the fly, based on ever-changing conditions. For example, typing in the web address of a site and landing on the home page is a condition for which a web developer might program the display of dynamic data to occur.
The developer might want the content of the home page to be displayed in a random order so that the page appears different each time it is called. He or she might also might want to do something like displaying the most recent content added to the database or even allowing visitors to customize, to some extent, their visitor experience. Personal preferences of each visitor would determine what content is displayed and how that content appears to them. This is another real-world example of the generation of dynamic data.
Web developers use programming languages for the coding of scripts to achieve dynamic data. If a website is data driven, the developer will have to work with a database. The developer can write queries to add, update, delete and combine information in the database to create dynamic data that will be displayed for all possible scenarios.
A database is not always what is behind data that is dynamic. The time changes from minute to minute, and the date changes each day. Simple scripts can be written to achieve the display of the current time and date on a website that consists of static or unchanging data.