Public Relations is not about one thing. It's about three things.
Awareness is a simple ping: they have that feature on that car now; they just opened that long awaited restaurant; they're running a promotion.
Trust is far more complicated. Trust comes from experience, from word of mouth, from actions noted. Trust, also seems to come from awareness. "Did you read that review in the magazine" is a debatable way to claim trust, but in fact, when people are more aware of what you do, it often seeps into a sort of trust.
And action is what happens when someone actually goes and buys something, or shows up, or talks about it. And action is as complex as trust.
Action requires overcoming the status quo. Action means that someone has dealt with the many fears that come with change and still does something.
Many people reading this are aware that they can buy a new gadget, and might believe it's worth the effort, but don't take action.
Many people reading this are aware that they can visit a foreign land, read a book (no - write a book), start a business... but action is the difficult part.
Action is quite rare. For most people, the story of 'later' is seductive enough that it appears better to wait instead of leaping.
As a marketer, then, part of the challenge is figuring out which of the three elements you need the most help with, and then focus on that...