All pay-per-click engines have guides as to the style of your ads and the relevancy which determine what words you can bid on for your website.

You should use correct English grammar and a normal writing style, as you would in an essay or letter. Avoid excessive capitalization, exclamation marks, or superlatives (don't use "CHEAP", "Buy Right NOW!", or "We’re the BEST!")—the editors will change or reject ads that attempt to squeeze these through the style guidelines.

Relevancy rules are based on the idea of providing a positive and relevant search experience for the consumer. To decide if a keyword is relevant to your business, imagine that you are a consumer who knows nothing about your business—would you be surprised to see your ad display for that keyword (because it doesn’t seem relevant to the search)? Would you be able to understand why it is relevant by clicking through to your website? If the answer is "no" to either, then it seems likely the keyword is not relevant, and even if you are allowed to bid on it, it will likely produce poor results. PPC can be very expensive and even wasteful if you simply bid on any term that comes out of the top of your head. People do not necessarily think the way you do, and may use other search queries to find what you offer.