When you add a snippet in e.g. a press release, this text will not be included in the publication itself.
The snippet will be displayed in list views, like for example search engine results, social media feeds, on Mynewsdesk Stories or the front page of your newsroom. Moreover, it will be included in the email alerts that are sent out to followers of categories.
If you want the snippet to appear in the press release, you need to also include it in the body text, for instance as a preamble. Please note that the snippet field does not have any impact on the ranking in search results (SERP).