How does PG Inheritance work?

How does Postgres internally handle inheritance under the following
scenario?
Using sample tables similar to a previous post:

 CREATE TABLE employee(id primary key, name varchar, salary numeric(6,2));
 CREATE TABLE programmer(language varchar, project varchar) INHERITS
(employee);
 CREATE TABLE representative (region varchar) INHERITS (employee);

Let's say for example's sake, there are 10 million rows of PROGRAMMER data
but only 100 rows of representative data.  Will a query (select, update,
insert, etc) on the REPRESENTATIVE table take a performance hit because of
this?

It seems like the child-table is really not concrete. It seems like it is
just a "pointer" to certain rows in the parent table which is then able to
discern which inherited "table-type" it is.

Thanks,

Aaron