Don't be discouraged, you are by far not the only one to get a little confused on rebloom. The AHS definition of rebloom to me certainly leaves a lot unexplained...I would love to see a much more detailed explanation and it would be nice if the explanation showed examples of each type of rebloom.
It helps me to think of roses and how they send up a first "flush" of blooms, then rest and send out another "flush" of blooms. So, daylilies send up a first flush of scapes, they bloom, then the plant rests for a period and later sends up a second flush of scapes, etc. That is one type of rebloom.
Some daylilies send up a scape and the first buds bloom and when the first buds have finished blooming new buds develop further up on the same scape (bud building). These new buds tend to put on much less of a show, (one flower at a time) but do extend the season by showing some bloom over a long period of time.
Then there is "instant rebloom" when the daylily sends up a first flush of scapes and blooms, and before the first series of scapes can finish blooming the daylily produces new scapes that start blooming. This process may continue for some time, and I think that is what is referred to as continuous rebloom.
That is about the best I can explain rebloom as I understand it.
I do have varieties in my garden that demonstrate at least one of each of the above mentioned types of rebloom.
'Optical Delight' was one of the first daylilies in my garden to bloom this season, and it is still blooming !
'Ming Porcelain' had the earliest blooms on what I would consider to be a pre-bloom scape, and now it is on its second set of rebloom scapes.
I find it easier to understand rebloom if I think of it mainly as a series of repeating blooms or a period or a series of new scapes being displayed.
