Now the words "SQL Standard" mean ISO/IEC 9075 Information technology -- Database languages -- SQL ... 2016" or more briefly SQL:2016. I am no longer a member of the committee, I don't have the latest copy, but I believe these are the notable changes.
The LIST_AGG function
The example I've seen (credit to Markus Winand) is
SELECT grp, LIST_AGG(val, ',') WITHIN GROUP (ORDER BY val) FROM t ORDER BY grp;
and the result is supposed to be: take each "val" value and
concatenate it with the previous one, separating by "," as
Notice a similarity to GROUP_CONCAT() in MySQL/MariaDB