I have been using Microsoft SQL Server 2017 for a while (just DDL and DML) and recently decided to install JetBrains DataGrip because I thought it was another DBMS but with dark theme.
When I try to create a new database it tells me to assign a host/user/password/port and I cannot do anything because it can't "connect to the database". I've been using Microsoft SQL Server Management Studio 2017 and never needed to assign a port/password/host or anything? I just created a new database and started adding/filling tables. How does JetBrains DataGrip work?
I noticed that on the JetBrains DataGrip page it doesn't say it's a DBMS, it says it's a "Database IDE". I cannot seem to find information about this on the web.
When considering a RDBMS such as SQL Server, the core component is a service/engine which acts as an interface between the database (files) and end users or applications allowing database functions to be carried out.
SSMS (SQL Server Management Studio) is just one of many possible end users of the SQL Server Database, and happens to have be part of the SQL Server software suite. It should not, however, be confused with the database itself as SQL Server operates perfectly happily without ever seeing SSMS.
Any form of user interface tool for a database needs to know how to connect to the database it is going to manage. In your case you most likely installed the entire software suite with default settings and as such didn't need to know what they were. JetBrains DataGrip however does need these settings.
You can find out what your specific settings are by running the SQL Server Configuration Manager.