For example, when a software company that makes a program to protect against electronic invasion of privacy argues that the internet is becoming dangerous because of electronic spying, they're biased. Their argument is directly tied to their own business success. The argument is likely to be based in part on the company's interests, not on the interests of the audience. Similarly, an argument based on the assumption that the government is out to get most citizens would be biased because it's based on a basic idea that most people don't share. If the author first persuaded readers that the government is out to get people, then the rest of the argument could work.
Arguments run into other problems due to logical fallacies.
These are ways of presenting ideas and using evidence that can seem persuasive at first but don't really make a good case. For example, if a writer argues that the President's tax plan is a bad idea because he's not trustworthy, that's a logical fallacy. The President's trustworthiness has nothing to do with whether his tax plan will work.