what are the Streaming APIs

basically I want to understand both high level and also technical point of view as what constitutes a streaming API, there are all sorts of data available but I could not find a satisfactory explanation of streaming API, also how does it differ from general APIs (REST if applicable)

PS:I am not asking about multimedia streaming.

Kind of a vague question. I guess streaming usually means one of the following (or a combination)

• downloading data for immediate consumption, rather than a whole file for storage, potentially with support for delivering partial data (lower quality, only relevant pieces etc), sometimes even without any storage at all in between producer and consumer
• a persistent connection that continues to deliver new data as it becomes available, rather than having the client poll

A good example (for the first pattern) are streaming XML parsers (such as SAX). They allow you to handle XML data that is too big to fit into memory (which a DOM parser likes to do).