it is the triad formed by stacking a major third and a minor third on the 1st note of the c major scale. That is, the 1st, 3rd and 5th notes of the major scale, played simultaneously Those notes are...
Strictly staying in the C major scale there can be no flat or sharp tones in the chord.
In popular music, it is common to use the chords C, Dm and G, also, F, Am, and Em.
It is actually the Bridal March from Richard Wagner's "Lohengrin". I haven't seen the opera, but assume the original lyrics (sung by the bridal chorus) are in German.