Database is the collection of information or data that any organization can be easily accessed, manage and update.
Data is organized into rows, columns and tables, and it is indexed to make it easier to find relevant information. Data gets updated, expanded and deleted as new information is added. Databases process workloads to create and update themselves, querying the data they contain and running applications against it.
Columns: a column is a set of data values of a particular simple type, one value for each row of the database. A column may contain text values, numbers, or even pointers to files in the operating system.
Indexes: A database index is a data structure that improves the speed of data retrieval operations on a database table at the cost of additional writes and storage space to maintain the index data structure. Indexes have also an architecture and different types and methods, I would talk deeper about this in another session, for example, Non-clustered Index, Clustered and types as well as Primary, bitmap etc...
Invented by Edgar F. Codd at IBM in 1970, is a tabular database in which data is defined so that it can be reorganized and accessed in a number of different ways. Relational databases are made up of a set of tables with data that fits into a predefined category. Each table has at least one data category in a column, and each row has a certain data instance for the categories which are defined in the columns.
SQL is an abbreviation for structured query language. SQL is a standardized query language for requesting information from a database. The original version called SEQUEL (structured English query language) was designed by an IBM research center in 1974 and 1975.
A distributed database is a database in which portions of the database are stored in multiple physical locations, and in which processing is dispersed or replicated among different points in a network.
A cloud database is a database that has been optimized or built for a virtualized environment, either in a hybrid cloud, public cloud or private cloud. Cloud databases provide benefits such as the ability to pay for storage capacity and bandwidth on a per-use basis, and they provide scalability on demand, along with high availability.
NoSQL databases are useful for large sets of distributed data, are effective for big data performance issues that relational databases aren't built to solve.
Microsoft SQL Server, Oracle Database, IBM DB2 and MySQL are the top RDBMS products available for enterprise users. DBMS technologies began in the 1960s to support hierarchical databases, and they include IBM's Information Management System and CA's Integrated Database Management System.