Some of the differences between public relations and advertising have been explained in this book. Among them are that public relations aims to inform, educate and create understanding, whereas advertising seeks to persuade and sell; public relations needs to be unbiased if it is to be credible, but advertising is inevitably biased if it is to succeed; public relations has to deal with unfavourable as well as favourable situations, quite unlike advertising which promotes selling points; the biggest single cost in public relations is time, but in advertising it is the cost of space and airtime plus production. Another major difference is that while most advertising personnel are engaged in advertising agencies, the majority of PR practitioners are employed in-house.