Standard candles are astronomical objects with known luminosity, allowing astronomers to measure distances in the universe. By comparing their intrinsic brightness to how bright they appear from Earth, scientists can calculate how far away they are. Common examples of standard candles include Cepheid variables and Type Ia supernovae. These objects have consistent brightness patterns, making them reliable for distance measurements. Using standard candles helps improve our understanding of the universe's expansion and the scale of cosmic structures.