PostgreSQL and default Schemas
What you're seeing is mostly one user interface's way of displaying the structure of a PostgreSQL database.

If you were using pgAdminIII, which is just another administrative interface, each database would usually show two "catalogs": information_schema and pg_catalog. It would also have a schema named "public".

Database objects named "pg_*" are system objects. The pg_toast schema holds TOAST storage for large tables. 

The information_schema views are part of the SQL standard. They're supposed to provide a vendor-independent way to determining information that's stored in vendor-specific system tables.

You can make a good case for not exposing every namespace as if it were a user-level schema. (Internally, these are namespaces. Try select * from pg_namespace;.)  The only schema in a newly created database that really matters to users is "public".