Tritones and Sub5s sound complicated but they are super cool and super fun.

I’m in search of the clearest explanation in a paragraph and in a video. Can anybody help?
My best shot: tritone substitution is replacing one chord with another three whole steps
up or down from the original. Example: replacing a G7 chord with a Db7 chord.
Typical context: replacing the V7 chord in the standard II V I sequence in jazz with
the chord three whole steps up or down. This works because both the orignal
chord and the new chord share two critical notes that in both cases resolve by
half steps. For example, the G7 chord consists of G, B, D, F and the Db7
consists of Db, F, Ab, and Cb. But Cb is the same as B. So, two notes in common:
F and B.  In the V to I progression both the F and B resolve down a half step.
Annoyingly technical, but the results are super cool.
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