An M-type star is of the M-class, a spectral class for cool stars including red dwarves (M dwarves) which are main sequence stars, and red giants, which are beyond the main sequence. The common element is the temperature, which is less than other main sequence stars. They all have very weak hydrogen absorption lines.
Some red dwarfs are Proxima Centauri, Barnard's Star, Lacaille 9352, Lalande 21185, Ross 154, Ross 248, Wolf 359, and Gliese 581.
|1-10 trillion years||main-sequence lifetime|
Some characteristics of M dwarfs (mass, radius and luminosity as fraction of the solar values):
These classes are often followed by a V, e.g., M7V, indicating a main sequence (dwarf, as in non-giant) star.
An example red giant is Betelgeuse. The red giant phase lasts on the order of a billion years. Their absolute magnitude is brighter because of their size.