It implies that these features are more about showmanship than substance.
Here are some ways the idiom is used:
* "The new car has all the bells and whistles, but it's way too expensive." (The extra features are fancy but make the car unnecessarily expensive.)
* "The presentation was full of bells and whistles, but it lacked any real substance." (The presentation was visually appealing but didn't convey meaningful information.)
* "We don't need all the bells and whistles for this project, just a simple and effective solution." (Focus on functionality over unnecessary extras.)
The idiom's origin is uncertain, but it likely comes from the idea of decorative elements being added to objects like tools or machines to make them more visually appealing.