I think it's a synonym for a class.
"abstract" == "dealing with a subject in its abstract aspects"
"data" == "information in numerical form that can be digitally transmitted or processed"
"type" == Java type
It's a way of combining attributes to represent something meaningful in your software model. If I decide to combine two Strings to create a Name class, I'd say that I'm abstracting that detail in my model and just dealing with a Name. It's easy to see how I might do it a different way and add more detail (e.g. ,salutation, middle name, suffix, etc.). It's all still a Name to me.
Collection, Bag, and List are examples of data structures. (Others are Map, Dictionary, Tree, Set, Queue, Stack, etc.) Any good book on the subject will tell you what the differences are. Worth a read.