

If you don’t know SQL at all, that is where you will need to start.
If you know enough to get the idea and are ready to go further than this might help https://postgis.net/documentation/training/
and this is the best book on the subject: PostGIS In Action https://postgis.us/
Postgresql is the database, Postgis is an extension. All modern databases are spatial, but postgis adds so much more. For example, maybe you reproject something with ArcGIS. In Postgis you simply select with the new projection on the fly.
You can clip, linear reference, compare, etc, all the spatial functions you do in a gis tool. Raster, vector, point data, etc.
When you grow up and become an adult we can talk. You clearly have no idea.
Same thing they said about computers like I said…