Best possible explanation
"Yes streaming is a form of downloading.
Normally a download must be complete before you can use or access a file. However when you stream a file from websites such as Youtube, the file can be viewed as it downloads.
While at Youtube take a look at the time slide bar. You will notice the red bar "loading". That bar is a visual representation of how much of the video has already downloaded.
When a file is streamed it is saved into the Internet Temporary files. So the next time you clear your cache, these files are deleted."
So , streaming is actually downloading data and it will be counted as data bandwidth being used. in fact almost everything you do on the web = downloading. pretty much. And the size of video depends on the quality and the length of the video. A 10 min video from Youtube takes 40 MB with non HD content.
