> Let's get the users last name.

    SELECT json_content ##> {person, last_name} FROM mytable;

> The #> or #> is the JSON path navigator with the difference being #> returns JSON and the ##> returns the JSON text value.

That should be #>> (two ">"), not ##> (two "#").

The official docs are really good and they include a number of inline examples showing the difference between the operators: https://www.postgresql.org/docs/current/functions-json.html

The bottom example is missing a colon on the cast as well:

> SELECT json_content FROM mytable WHERE json_content @> '{"status": "Awesome"}':jsonb;

Should be two colons ("::") for an explicit cast: '{"status": "Awesome"}'::jsonb