A cold stream does not start producing values until one starts to collect them. A hot stream on the other hand starts producing values immediately.

I would recommend to read below to understand hot and cold steams with usage:

https://balwindersinghrajput.medium.com/complete-guide-to-livedata-and-flow-answering-why-where-when-and-which-6b31496ba7f3 https://developer.android.com/kotlin/flow/stateflow-and-sharedflow

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Cold vs Hot streams

Well, I really struggled with this concept because it is a little bit tricky. The main difference between cold and hot happened to be pretty simple: Hot streams produce when you don’t care while in cold streams, if you don’t collect() (or RxJava-s equivalent subscribe()) the stream won’t be activated at all. So, Flows are what we call cold streams. Removing the subscriber will not produce data at all, making the Flows one of the most sophisticated asynchronous stream API ever (in the JVM world).