What is the difference between a press release and an advertisement?

The simple truth is that a Press Release is NOT an advertisement, it
is news. If you write your press release in a style that resembles an
advertisement, it will simply be discarded.

Here are some tips to make sure your press release does not read like
an advertisement:

1)Follow a standard press release format -Journalists and editors have 

become accustomed to a standard press release format. It is important

to follow the standard formatting so that journalists and editors can quickly

find the information they are looking for.

2)Write your press release from the third person point of
view. Instead of words like "I" or "we", use your name "Mr. Smith, CEO
of XYZ Company" or company name "XYZ Company"

3)Don't ask for the sale. You should never use a press release to ask for a sale. 

Statements such as "Visit our web site to order XYZ product" or "Visit our web
site to sign-up for our newsletter" should be avoided.
An example of the above statements in press release format would be
"Customers interested in purchasing XYZ product can visit XYZ
Company's web site located at…".