PostgreSQL is a free open-source Relational Database Management System (RDBMS). Its name is derived from the Ingres database previously developed by the University of California Berkeley. The SQL name was added to the prefix to indicate support for SQL. This database follows all ACID properties such as longevity, shielding, consistency and atomicity. It has updatable stored procedures, foreign keys, views, triggers and materialised views. These features are updated regularly with new versions.  
The database management system can handle various workloads, including databases, internet services, individual computers and systems used simultaneously by different users. It is also used as the default database for the MacOS server and is available on Windows, OpenBSD, FreeBSD and Linux.  

It also has a Multiversion Concurrency Control, which is used to manage concurrency by making each transaction a snapshot of the database. This means that changes to a single transaction do not affect other transactions. Using this feature also eliminates the need for read locks and maintains all the ACID properties mentioned above. 

PostgreSQL also provides three levels of transaction isolation, namely: Read Committed, Repeatable Read and Serialisable. It is immune to Dirty Reads and requests to Read Uncommitted. Isolating transactions still results in Read Committed. It also uses Serialisable Snapshot Isolation (SSI) methods that support full serialisation. 

Common use cases of PostgreSQL

Below are some use cases for the database management system. It is a strong Database for LAPP Stack. LAPP Stack stands for Linux, Apache, PostgreSQL and PHP (Perl and Python). In this case, this RDBMS provides a robust database for the back-end to support dynamic internet applications and websites.  

Geospatial database 

When the PostGIS extension is added to PostgreSQL, the database can support geospatial databases used for GIS (geographic information systems). 

Support for multiple languages 

The database supports the most popular programming languages such as Java, Python, C#, Ruby, Tcl, Go, Perl, JavaScript node.js, C and C+. The database is also used as a primary database to support various products and applications.  
Although it is a free database, it also offers many enterprise-level features that you would find in premium database management systems. These include table inheritance, custom types, asynchronous replication, multi-version concurrency control (MVCC), nested transactions (savepoints). Other features include a sophisticated locking mechanism, table inheritance and referential integrity of foreign keys. This database is also extensible, allowing you to define your data types, function languages and index types. You can also add a custom plugin to enhance all the features of the database.