What is the 180 rule in Spain?

Could you please elaborate on the concept of the 180 rule in Spain? I'm quite intrigued to understand its significance and application in the context of Spanish laws or customs. Could you provide a brief explanation of its origins, and perhaps some examples of how it might be implemented in real-world scenarios? Also, is this rule widely known and observed among the Spanish population, or is it more specific to certain regions or industries? Thank you for your time and explanation.