Final answer:
The symbol |<------->| represents a double-sided arrow line, indicating an infinite extension of a line in both directions in a coordinate system.
Step-by-step explanation:
The symbol |<------->| represents a double-sided arrow line in a coordinate system. This type of line often indicates continuation in both directions and is commonly used in mathematics to symbolize a line that extends infinitely in both the horizontally to the right side of the coordinate system and horizontally to the left side of the coordinate system. It is important for geometric representations and is not to be confused with a solid line that typically represents a finite segment or a dashed line which may represent something that is not physically present or is an extension beyond a particular region.