An example of a dominant chord would be; C7
Which consists of chord tones; C,E,G,Bb
Root of the chord is; C
Major 3rd above the root is; E
Perfect 5th above the root is; G
Minor 7th above the root is; Bb
C,E,G,Bb 1,3,5,b7 (1, Maj3, P5, minor 7th).
Another way of thinking of this chord would be a Major Triad with the addition of a minor 7th from the root.
C Major triad would be; C,E,G add the minor 7th; Bb to these and you get a C7 (C dominant 7 chord) . Which is C,E,G,Bb.