"In Portal, the player controls the protagonist, Chell, from a first-person perspective as she is challenged to navigate through a series of rooms using the Aperture Science Handheld Portal Device, or portal gun, under the watchful supervision of the artificial intelligence GLaDOS. The portal gun can create two distinct portal ends, orange and blue. The portals create a visual and physical connection between two different locations in three-dimensional space. Neither end is specifically an entrance or exit; all objects that travel through one portal will exit through the other." "For example, a common maneuver is to jump down to a portal on the floor and emerge through a wall, flying over a gap or another obstacle. This allows the player to launch objects or Chell over great distances, both vertically and horizontally, referred to as 'flinging' by Valve. As GLaDOS puts it, 'In layman's terms: speedy thing goes in, speedy thing comes out.'"
Portal's Wikipedia page, accessed February 12, 2020