What a database is simply a repository of data. Data are pieces of information that is important for some purpose; business or otherwise. Typically, you would need to add to the repository, pieces of data may need to be updated/ modified. When a piece of data has outlived its purpose, users would like to delete the same. A software system that lets you manage data and meet your needs as described is a Database. Examples of databases we are familiar with would be,
RDMS or relational databases are in popular use for storing such data in an enterprise. These use an organization known as tables. These tables themselves are organized in a manner familiar to all of us as rows of information that has columns to store related pieces of data for that row. Tabular organization helps searching flexibly. Relational databases allow relating multiple tables together for the data finding and manipulation purposes. This is something we do at personal levels too. Our telephone book is a prime example of this organization. A name with first name and second name, telephone number, possibly the address goes into such a phone book. Often important dates like birthday, wedding anniversary and other information are included. One such entry will be a record in a particular database row. Each of the items will go into a column that is common to all the records. Some well-known and popular databases are Oracle, SQL Server and MySQL.
Sometimes the database may be organized in a distributed manner. The data are placed at different physical locations and parts of the database may have copies at different spots on the network.
An associated concept to a database is a database management system. These database products let you store multiple databases and have very large capacities to do so. In a typical business, you may need to store data about customers, sales made, details of your inventory and so on. There is a need for a management process to let the diverse databases work properly. The DBMS or the database management system lets read or write access in a disciplined manner. Authorization of users is managed by the system. Analysis of usage and performance are also provided. Then, of course necessary types of reports are usually provided by these database management systems.
Database and database managers are available on the full spectrum of systems; from mainframes to personal computers and everything in between. Major difference is in the capability of the amount of data that could be handled by the different versions of each product. In all these incarnations of the database products, it is the relational database that is currently used predominantly. All the products use a form of a query language that has become an ANSI as well as ISO standard. This is known as Structured Query language or SQL. This language lets the users specify queries to find data, manipulate or update them. It has commands for changing the structure of the database too.