These two constellations are high overhead in the northern hemisphere during the fall and winter months. The brightest stars of Andromeda form a cornucopia shape curving away from the Great Square of Pegasus. Two strings of dimmer stars form the irregular "arms" of the princess Andromeda.
The three brightest stars of Triangulum form the shape you would expect.
Each of these constellations is home to a well-known and nearby spiral galaxy. M31, the Andromeda Galaxy, can be seen with the naked eye even under moderately light-polluted skies if you know where to look. M33, the Triangulum Galaxy, has also been glimpsed with the naked eye by many people, but this requires very dark skies.