PR is a broad category, but what I mean is that someone (news, magazine, big blog...) publishes something about your company, which you don’t pay for. Something positive if possible. Usually, it has an immediate effect on your web traffic, and hence on your sales.
Most of our smaller clients don’t consistently communicate with media, because they think they have zero chance of getting there (without paying for ads). But it is not valid. It is not easy, but there are best practices that can help (there will be more about in some of the next Notes). To choose the right medium is very important. Having CNN reporting about you would be nice (except the case when you e.g., kill a lot of people...). However, usually, it could be much easier and much more efficient to get to a local or industry-specific newspaper.
In the past, I served as the CEO of a local healthcare company, and we were publishing articles (not paid) in local news. Local newspapers often struggle with the lack of content, so it was relatively easy to get there with a non-commercial text. Moreover, the target group matched exactly our needs, so we had a promotion at no costs.