A Pirate is a pilot who hunts (and/or camps for) other pilots in low-security (0.4 or below) space, then attacks them for fun and/or profit. Some pirates also operate out in 0.0 space as well, though the definition of 0.0 raiding as “piracy” is disputed by some. Some pirates roam systems looking for players in belts, while others scan probe missions or engage in gatecamping. Bottleneck Systems that many people have to travel through are favourite locations for such camps.
Like historical piracy, piracy in EVE is distinct from other forms of EVE PvP by virtue of being non-politically motivated, unsanctioned by any sovereign nation or organization (NPC or Player Controlled), and is not commissioned or prearranged by business agreement.
In other words, piracy is indiscriminate PvP.
Some pirates are profiteers, ransoming and/or looting prey for cash. Others do it merely out of a love of PvP, while still others are simply low sec griefers.
Most pirates have low security statuses, typically lower than -5.0 (making them outlaws, or “flashy-reds”) However, some intentionally maintain a high security status to give other players a false sense of safety.