Transactional DDL

Hi,

A few days back, it was commented by someone in the community that Postgres has
this Transactional DDL feature.
What I understand about Transactional DDL is something like this:

begin
       --ddl 1
       --ddl 2
end;

I believe that if a database supports transactional ddl then ddl1 and ddl2 would commit together as a batch
And
If a Db doesn't support this transactional DDL feature then ddl1 executes and commits without even caring about ddl2. Right?

~Jas