Answer 1

It's just telling that you're using default lc_collate for this column.

But what's the default collate? Use SHOW to discover that.

SHOW lc_collate;

PostgreSQL allows to create columns with different types of collation:

CREATE TABLE collate_test
(
  default_collate text, --Default collation
  custom_collate text COLLATE pg_catalog."C" --Custom collation
);

Did you see the difference?

More info about collation is on docs:

The collation feature allows specifying the sort order and character classification (...)