When you’re starting out on a simple web application, eventually1 you will reach the point where you need to store some form of persistant data. Basically, you have three options2:
- Store the information in flat files on the file system
- Store the information in a database (MySQL, SQLite etc)
- Store the information in a key/value store (mongoDB, reddis)
There are all manner of pros and cons to each, in particular how easy they are to get started in, how well they fit the data you are using, and how well they will scale horizontally (adding more machines rather than bigger ones).