Parallel lines are straight lines that run alongside each other and never meet, no matter how far they are extended. They maintain a constant distance apart, which means they will always be the same length apart at every point. You can often see parallel lines in everyday life, such as the edges of a ruler or the tracks of a train. In geometry, parallel lines are usually represented with arrows on one end to indicate that they will never intersect. They are an important concept in various fields, including architecture and engineering, where maintaining consistent distances is crucial for design and stability.