What is Bitrate, CBR, VBR ?

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What is the bitrate?
In telecommunications and computing, bit rate (sometimes written bitrate) is the number of bits that are conveyed or processed per unit of time.
Bit is the unit of information.  Remember that 1 byte consists of 8 bits. Video data rates are given in bits per second. The data rate for a video file is the bitrate. So a data rate specification for video content that runs at 1 megabyte per second would be given as a bitrate of 8 megabits per second (8 mbps). The bitrate for an HD Blu-ray video is typically in the range of 20 mbps, standard-definition DVD is usually 6 mbps, high-quality web video often runs at about 2 mbps, and video for phones is typically given in the kilobits (kbps).
 
Understanding bitrate in video files
It’s important to understand how the bitrate control corresponds to video quality and the file size. At the same bitrate, video in a newer codec such as H.264 will look substantially better than an older codec like H.263. Another consideration is that variable bitrate (VBR) encoding will produce better image quality than constant bitrate (CBR) in most applications.

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