The stellar main-sequence is a strip that cuts diagonally the Hertzsprung-Russell diagram, a star's plot of stellar color versus brightness. The main feature of main-sequence stars is that they burn hydrogen. In this group the K dwarfs, or orange dwarfs, are intermediate stars in size between red M stars (red dwarfs) and yellow G stars. Their mass is between 0.5 and 0.8 times the Sun's mass and surface temperature is bewteen 3900 and 5200 K.
In the last few years these type of stars have become particularly interesting to astronomers, as they appear to have the characteristics to host life-as-we-know:
