A D7sus4 chord contains the notes D, A, C, G. It is built from the dominant 7th suspended 4th formula 1 - 4 - 5 - ♭7, with D as the root.
What is the difference between D7 and D7sus4?
D7 contains a major third (F♯); D7sus4 replaces it with the fourth (G). Both are dominant chords that pull toward G, but D7sus4 already contains a G, so the resolution is softer and more suspended — less of a sharp leading-tone tug, more of a gentle settle.