A media stream can be streamed either "live" or "on demand". Live streams are generally provided by a means called "true streaming". True streaming sends the information straight to the computer or device without saving the file to a hard disk. On-demand streaming is provided by a means called "progressive streaming" or "progressive download". Progressive streaming saves the file to a hard disk and then is played from that location. On-demand streams are often saved to hard disks and servers for extended amounts of time; while the live streams are only available at one time only (e.g., during the football game). Streaming media is increasingly being coupled with use of social media. For example, sites such as YouTube encourage social interaction in webcasts through features such as live chat, online surveys, user posting of comments online and more. Furthermore, streaming media is increasingly being used for social business and e-learning. Due to the popularity of the streaming media, many developers have introduced free HD movie streaming apps for the people who use smaller devices such as tablets and smartphones for everyday purposes.