The term "long line" can refer to a number of different things depending on its context.
In general, it could mean any extended or elongated object or structure such as a rope, wire, cord, or even a queue (a waiting line). It may also be used in reference to something that is lengthy or extensive, like a long speech, book, or journey. In some cases, "long line" can refer specifically to a type of fishing gear consisting of a main line with multiple branch lines attached for catching various species of fish.
Please provide more context so I may better assist you in understanding the phrase as it relates to your specific inquiry.