Two Tables That Share Data?

I want to create a separate table in my database called 'dept' and
basically identify each unique department in my company represented by
numeric code for example:

Code:
CREATE TABLE dept
(
id SERIAL PRIMARY KEY,
name VARCHAR(50) UNIQUE NOT NULL,
email VARCHAR(50) UNIQUE NOT NULL
);

So this table should look something like:

Code:
 id |           name           |       email
----+--------------------------+--------------------
  1 | Information Technology   | it@myco.tld
  2 | Configuration Management | cm@myco.tld
  3 | Facility                 | facility@myco.tld
  4 | Software Development     | software@myco.tld
  5 | Finance                  | finance@myco.tld
  6 | Logistics                | logistics@myco.tld
  7 | Inventory                | inventory@myco.tld
(7 rows)

Now I'm going to make a new table called 'employees' & there is going
to a field called 'dept' which will have a value from the 'id' field
in the 'dept' table. My question is how does one traditionally
configure this in SQL?

When I create my employee table, what data type do I use to create the
'dept' field? It will only be storing a low numerical value since I
only have less than 20 physical dept records. Do I need to create a
foreign key constraint against this? I'm expecting the data to look
like this:

Code:
 id |    name     | dept |      email      |    hire
----+-------------+------+-----------------+------------
  1 | James Smith |    5 | jsmith@myco.tld | 2011-04-19
(1 row)

As you can see the user James Smith is in dept. #5 which is my finance
dept. Can someone please point me into the right direction on how to
get this database working as mentioned above?