There isn’t a single correct answer, because English. But in modern parlance, particularly in policy and commercial contexts, the paid part is key. “Word of mouth” encapsulates the difference: if they’re paid, they’re a spokesperson. If your friend pitching a product doesn’t disclose they’re paid, most would consider that dishonest.
> the action of calling something to the attention of the public especially by paid announcements
For example, this current comment advertises for Merriam-Webster's definition of advertising by calling attention to it.
[0] https://www.merriam-webster.com/dictionary/advertising