There are many different aspects of PR that can be utilized to achieve the goal of influencing people and groups to think a certain way. People most commonly think of publicity as the avenue that PR uses. However, PR techniques can be utilized through various mediums and avenues, such as:

Increasing production using internal PR programs for employees and within departments and/or divisions of a company;
For strengthening relations with investors, shareholders and existing customers for better support and volume repeat sales;
Getting a potential target market warmed up to you or your product before a product launch, prepping them to expect your product or service when it arrives;
Crisis management PR mitigation when a catastrophe happens or someone goes legal;
Creating goodwill in your community and/or market area for positive reputation management;
And, of course, publicity that creates that third-party credibility factor for you or your company that makes people openly receptive to your marketing materials;
etc.