Streaming is the continuous transmission of audio or video files from a server to a client. In simpler terms, streaming is what happens when consumers watch TV or listen to podcasts on Internet-connected devices. With streaming, the media file being played on the client device is stored remotely, and is transmitted a few seconds at a time over the Internet.
What is the difference between streaming and downloading?
Streaming is real-time, and it's more efficient than downloading media files. If a video file is downloaded, a copy of the entire file is saved onto a device's hard drive, and the video cannot play until the entire file finishes downloading. If it's streamed instead, the browser plays the video without actually copying and saving it. The video loads a little bit at a time instead of the entire file loading at once, and the information that the browser loads is not saved locally.
Think of the difference between a lake and a stream: Both contain water, and a stream may contain just as much water as a lake; the difference is that with a stream, the water is not all in the same place at the same time. A downloaded video file is more like a lake, in that it takes up a lot of hard drive space (and it takes a long time to move a lake). Streaming video is more like a stream or a river, in that the video's data is continuously, rapidly flowing to the user's browser.
How does streaming work?
Just like other data that's sent over the Internet, audio and video data is broken down into data packets. Each packet contains a small piece of the file, and an audio or video player in the browser on the client device takes the flow of data packets and interprets them as video or audio.
Sending video over the Internet, as opposed to sending text and still images, requires a faster method of transporting data than TCP/IP, which prioritizes reliability over speed.