Embargo is a term that referes to a specific time period when news organizations cannot air, nor publish news information that they have obtained.
This news embargo is often set from companies that are giving their products to the media, so they’ll create news about it, but not creating a review (often happens with tech YouTube channels that receive the newest model of a phone, they show it, tell their audience what the company promisses but don’t have the right to share their opinion).
Once the product is released to for purchase, the reviewer (and the news channels) have the rights to publish whatever they want about it.
In more serious matters, if details of the President’s speech are released early to the press, they are not allowed to release this information before the embargo has been lifted, which usually happens after the speech was given.
