Explain what is meant by the term 'cold stream' in the context of programming and streaming data.

A "cold stream" in programming is a data stream that does not start generating or transmitting values until a consumer subscribes to it. That is, data is not created in advance but only upon request. This differs from "hot streams," which generate data regardless of whether there are subscribers.

For example, in Kotlin Flow, a cold stream produces values each time a new subscriber joins, allowing the same stream to be reused for different consumers without losing data.