An IRA, or Individual Retirement Account, is indeed a retirement plan. However, it's not a qualified plan. Instead, IRAs are described in Section 408 of the Tax Code and have their own set of rules. One significant difference between qualified plans and IRAs is that qualified plans are established by businesses, while certain types of IRAs -- traditional or Roth IRAs -- are established by individuals. That means you can set up a traditional or Roth IRA for yourself, whether or not your employer has established a qualified plan for you at work.
Other types of IRAs, known as SEPs and SIMPLE IRAs, are for businesses and must be established by an employer. For example, the employer might be a corporation, a sole proprietor or a partnership. SEPs and SIMPLE IRAs permit larger tax deductions than do traditional or Roth IRAs.