The Aperture Science Handheld Portal Device or ASHPD as it is more commonly known as, is the key to success in both Portal and Portal 2. The device has the ability to shoot portals.
In Portal, the ASHPD is first found in test chamber 02. When found, the device can only create blue portals, but as Chell progresses through the game, she aquires a upgraded ASHPD, which can fire 2 linked portals (Blue and Orange).
The ASHPD is first aquired in the ruins of test chamber 02 after the ground around the ASHPD holder gives in to Chell's weight. Once again, it can only fire blue portals, but after the encounter with GLaDOS shortly after, Chell Recieves the Dual ASHPD.