The bit rate is the number of bits of data produced each second by a digital film camera. While there are two places to measure this, the traditional (and important) number is the bit rate correlated to that which is literally written to the digital storage medium.
This number differs from the maximum potential of the sensor (CCD) and governing microprocessor prior to the application of the compression codec. When a camera is enable to export directly to digital storage or over HDMI in an uncompressed raw format, this represents the maximum potential data rate produced by that camera. However, some cameras, such as the RED produce a compressed raw as the fully uncompressed raw would be an overwhelming volume, truly more than anyone would ever need.
Here is a table which provides a breakdown of some the industry standard bit rates, represented from the Wikipedia page (above):
16 kbit/s – minimum for a consumer-acceptable “talking head” picture
128–384 kbit/s – business-oriented videoconferencing
1.5 Mbit/s max – VCD quality (MPEG1)
3.5 Mbit/s typ — Standard-definition television quality (MPEG-2)
9.8 Mbit/s max – DVD (MPEG2)
8 to 15 Mbit/s typ – HDTV quality (MPEG-4 AVC)
19 Mbit/s approx — HDV 720p (MPEG2)
24 Mbit/s max — AVCHD (MPEG4 AVC)
25 Mbit/s approx — HDV 1080i (MPEG2)
29.4 Mbit/s max – HD DVD
40 Mbit/s max – Blu-ray Disc (MPEG2, AVC or VC-1)
At the time of this writing, 38.8 Mbit/s and above is used by Broadcasters for various formats.