general design pattern for smushing rows into one column
As others have mentioned, your goal is to denormalize the data and is not a usual use case for a relational database system, but it is certainly achievable. So if you really want to accomplish that, what you'd want to Google is something along the lines of &quot;PostgreSQL concatenate multiple rows&quot;. The goal usually is to create a comma separated values list (CSV or something of a similar structure).
Doing so actually led me to this StackOverflow answer on using the string_agg() function in PostgreSQL.
For historical reference, here is Erwin's example from the aforementioned StackOverflow answer, leveraging string_agg() to smush multiple Actor values into a single field per Movie row in a table of Movies:
SELECT movie, string_agg(actor, ', ') AS actor_list
FROM tbl
GROUP BY 1;

In your case, you'd want to JOIN your people to your tags table (via your junction table). From the above example movie would be equivalent to your person_name field, and actor would be equivalent to your tag_name field. A query likely similar to this is what you're looking for:
SELECT P.person_name, string_agg(T.tag_name, ', ') AS tag_list
FROM people P
LEFT JOIN peopleTagJunctionTable JT
    ON P.id = JT.person_id
LEFT JOIN tags T
    ON JT.tag_id = T.id
GROUP BY P.person_name;