postgis - Connect to PostgreSQL localhost in QGIS

I am fairly new to actively work with databases. I wanted to try out some stuff on my home computer where I have installed pgAdmin and PostgreSQL previously. I can connect to my localhost in pgAdmin but I can't do the same in QGIS. I just get an error message saying:

"Connection failed -  Check settings and try again"

I am new in this game and don't really know where to look for solutions. My database connection info is standard settings:

Name: postgres
Host:Localhost
Port:5432
Database:test

Any ideas what could be wrong?

Answer

I'll add an answer with a screenshot, as it will be easier to look at for reference.

Here is an example with the absolute minimum you would have to enter. It would connect to a database called twitter, and I would name that connection twitterDB. Note that it does not matter how you name the connection; this is just a name you give to your connection so you can refer to it later on (see last screenshot).

And here a screenshot of the actual database I am connecting to:

In QGIS your connection would show up like this:

Hit the Connect button, and if it worked, the Schema area will be populated, where you can then navigate to your tables.