Tonic

The three chords that all music is based on go by a variety of names. Tonic, Predominant, and Dominant are what they are commonly called in classical theory. 2-5-1 are the names given by jazz theorists. They create a plot, journey, and sense of direction. 

The tonic most times is a major chord and is the essence of stability and comfort. Creating release and portraying home. Play a Cmaj7 chord, it has C, E, G, and B in it. All white keys on the piano. The sense of calm is palatable. 

However the full effect is not realized without the other two chords.