What type of server is this?
PostgreSQL is an open source object-relational database management system (ORDBMS) distributed under a very permissive license, and developed by an active community.
There are a number of PostgreSQL-related services and software (https://wiki.postgresql.org/wiki/PostgreSQL_derived_databases), either open source or not, that are provided by other software companies. Here, we discuss how to recognize which one you are using.
It is not so easy to detect the variant of PostgreSQL from the name; many of the products and services involving PostgreSQL include the word Postgres or PostgreSQL.
However, if you need to check the documentation, or to buy services such as support and consulting, you need to find out exactly what type your server is, as the available options will vary.
If you are paying a license fee or a cloud service subscription, you will already know the name of the company you are paying, and of the specific variant of PostgreSQL you are subscribed to. But...