Matter is classified as Cold Dark Matter (CDM) because of the velocities of the particles. A CDM particle has sub-relativistic velocities because they are more massive than Hot Dark Matter and Warm Dark Matter. The masses of these particles are about 100 GeV. CDM particles do not interact via the electromagnetic force, but they do interact with the gravitation force. This is a key component into CDM being the most probable candidate for dark matter because we know that dark matter only interacts with the gravitation force. (4, 5)
Possible CDM candidates would be WIMPs. Discussed in more detail later in this report.