This is a disambiguation page, a list of pages that otherwise might share the same title. If an article link referred you here, you might want to go back and fix it to point directly to the intended page.
An example of illegal insider trading may be that you, as an assistant to the chief executive officer, learn that your company is going to be taken over before it is officially disclosed publicly.
Since insiders are required to report their trades, others often track these traders, and there is a school of investing which follows the lead of insiders.
Insider trading can make markets more efficient by increasing the amount of information that is known about the company, and can motivate outsiders such as analysts to increase their knowledge about the company.