Basically Database is collections of organize data. But technically Database is a software that can store date in organized structure and we can fetch data as our needs. Tow(2) types of database are commonly using in modern world.

1. Relational Database (MySql, Oracale, Postgress, Sqlite, Microsoft Access )
2. Non-Relational Database ( MongoDB , Realm)

Relational Databases:

MySql or  Oracale or Postgress or Microsoft Access can store data in organize structure. Difference is different company(like Google, facebook, IBM) launch different database software , different development language(like c, c++, java) and use different algorithm. But this 3 difference is internal difference. Developer or general people don’t deal with this 3 difference.

Generally a simple user use Microsoft Access or Excel as a database software by using GUI(Graphical User Interface) that's like table format. They can make table and insert data by fill up the table form.

But developers are generally use any relational database using some commands. By those command they create data table and insert data, delete data, update or fetch data. Using same commands,  you can perform Four(4) operations (insert, delete, update, fetch) in every database software(likeMySql, Oracale, Postgress, Sqlite).

So those commands are same for every database. Those commands call “SQL Query”.

If you know 4 queries (insert, delete, update, show) and some additional queries your can handle all kind of databases.