Definition - What does Insider mean?
Insiders include a company’s officers, directors, large stockholders of 10% or more of the company, and anyone who is in possession of non-public material information, along with the immediate family members of the same.
Testopedia explains Insider
It is assumed that insiders have the potential to access information that the general public cannot. For this reason, more stringent regulations apply to insiders. For example, insiders are limited in the amount of their company's stock that the can sell in any 90 day period and they are prohibited from short swing profit taking.