type buff extends ability?

I've seen this on jasscraft, so I tried adding a buff to a unit, It was not added. So the question is, does buff really extend an ability or warcraft's engine doesn't allow buffs to get added?
Another question, how can i use the type ability:
thanks guys!

Both.

Buffs use the same handle, but in a different way. They may be abilities as far as JASS is concerned, but they have different settings and so cannot be added.