Product placement is when a brand or product is integrated into a movie through an agreement between the filmmakers and the brand owners. The filmmakers don’t do it out of a desire to be nice to the poor brand owners either. Nope, ‘pay me’ they say. It doesn’t have to be cash. It could also be through some form of promotional exposure.
This is different to brand clearance where the filmmakers want to, or need to, include a brand in a movie and need to get permission from the brand owner. The filmmaker wants to use a brand as a creative tool.
From the viewpoint of the brand owner product placement is a tool to promote their brand. That doesn’t stop the filmmaker from being able to use it as a creative tool. Nor should it.
Either way once a brand is in a movie the audience has no way of knowing if the filmmaker got paid to include it or not.