Abaug9 is Ab, C, E, Gb and Bb. Start with and raise the 5th from to . You’ll also see this chord written Ab9♯5 or Ab9(♯5).
Hear what that one-note change does by comparing with Abaug9.
Only the 5th changes: E♭ rises a half step to E. The other notes stay in place.
When Abaug9 resolves to , that can rise another half step to .
Also written Ab9#5, Ab+9 or Ab9(#5).

Abaug9 is a dominant with its tension raised, so it still points at — harder than a plain seventh does. A plain dominant has two voices a semitone from home; an altered one has four, because every altered tone is also sitting a semitone from a note of Db. More voices leaning the same way is all "more tension" means here.
Contains Abaug9 and adds flat fifth.
The common shapes and the derived voicings come from different places, and both are explained in how this site is built.
Shows each chord the way this style would voice it, and marks which of its alternatives belong to the idiom.