The C lydian dominant seventh chord is a 5-note chord consisting of the notes C, E, G, Bb and F#.
You can see these notes highlighted in the interactive piano chart below.
The chord itself is often abbreviated as C7#11.
Interactive piano diagram for the C lydian dominant seventh chord
Chords that are a subset of C7#11. These contain less notes but all of them are included in C7#11.