Insider trading is the trading of a public company‘s stockor other securities (such as bonds or stock options) by individuals with access to non-public information about the company. In various countries, insider trading based on inside information is illegal. This is because it is seen as unfair to other investors who do not have access to the information.
Trading by specific insiders, such as employees, is commonly permitted as long as it does not rely on material information not in the public domain. However most jurisdictions require such trading be reported so that these can be monitored.