SMPTE 259M is a standard published by SMPTE which "... describes a 10-bit serial digital interface operating at 143/270/360 Mb/s."
The goal of SMPTE 259M is to define a serial digital interface (based on a coaxial cable), called SDI or SD-SDI.
There are 4 bitrates defined, which are normally used to transfer the following standard video formats:
References
SMPTE 259M Wikipedia(Text) CC BY-SA