Publicly traded companies in the United States are required to file a host of documents, and two of the most important, for investors, are the annual report and the 10-K report. Similar in many ways, these documents are designed to help inform potential investors or current shareholders about the company's performance.
A corporation's own annual report is usually a colored, professionally presented and marketable document intended for an audience of shareholders. There is typically a letter from the CEO and Chairman of the Board of Directors, review of the company's history and brief overviews of major company activity. While it can be considered a shorter version of the 10-K report, the design and intent of the annual report are distinctly separate from the 10-K. That said, you can still find a balance sheet, independent auditor's report, income statement and other very useful financial information inside of the annual report.
The 10-K report is submitted directly to the Securities and Exchange Commission, or SEC, and is not designed for easy consumption for investors. 10-Ks tend to be very lengthy and more difficult to access than annual reports. Ultimately, a 10-K report is a full description of the company's financial activity during a given fiscal year and a full rundown of risks, legal descriptions, corporate agreements, market performance and, sometimes, information that was not made public. 10-K reports also provide a full analysis of the relevant industry, the marketplace as a whole and individual business operations. The SEC has very strict guidelines on what information must be included and how it must be organized.