Once we get into chord progressions and ‘diatonic speak ... First, a jazzy II-V-I in C major would be Dm7-G7-Cmaj7. Then, if we move the G7 up a tritone/aug 4th/dim 5th, we will get a Db7.

The first 7th chord most of us learn is called just that ... You can convert this to a Dm7 by lowering the 3rd to F natural, or turn it into a major 7th by raising the C to C#.