Regressive or Humiliation?
ABDL means "Adult Baby Diaper Lover"
"adult baby diaper lover". A sexual fetish involving adults acting like babies and/or wearing diapers."
ABDL play; sexuality, loss of status or control, and change in role. In scenes that emphasize sexuality, the diapers would be used like other fetish objects or kinky toys. These encounters might not involve roleplay, and might not be formal scenes.
ABDL scenes emphasizing loss of status or control may use diaper humiliations in much the same way crossdressing humiliations would be used. The difference is that instead of masculinity, adulthood is being taken away. Diapers can also be used in other forms of loss, such as usurping the final control of bodily functions. There may be other forms of power exchange as well. There is little difference between an ABDL scene emphasizing loss and a more typical BDSM scene involving diapers.
Finally, there are ABDL scenes that emphasize a change in role. This doesn't involve a sense of loss, but another identity. The ABDL isn't a man deprived of adulthood, but a baby free to be itself. This is analogous to the transvestite who sets his own femininity free, or the sub who's bondage liberates him from responsibility. They may have less status or control, but there is no sense of loss.