All but dissertation
Okay kiddo, so you know how when people go to college or university, they have to write a really, really big paper at the end of all their classes called a dissertation? Well, sometimes people get pretty far in their studies and they finish all of their classes, but they don't finish their dissertation. When that happens, they are called "All But Dissertation" or ABD for short.
Basically, it means they did a lot of work towards finishing their degree, but they didn't quite finish all of it. It's kind of like if you were building a really big Lego set, but you got really close to finishing it and then you had to stop for some reason. You wouldn't have a completed Lego set, but you would have done a lot of work towards making it.
Now, being ABD isn't really a good thing or a bad thing. It just means that you haven't finished your degree yet. Some people might choose to leave school at that point and do something else, while others might keep working on their dissertation and eventually finish it up. Either way, they still have all the knowledge and skills they gained from their classes, so they haven't lost anything by being ABD.
Basically, it means they did a lot of work towards finishing their degree, but they didn't quite finish all of it. It's kind of like if you were building a really big Lego set, but you got really close to finishing it and then you had to stop for some reason. You wouldn't have a completed Lego set, but you would have done a lot of work towards making it.
Now, being ABD isn't really a good thing or a bad thing. It just means that you haven't finished your degree yet. Some people might choose to leave school at that point and do something else, while others might keep working on their dissertation and eventually finish it up. Either way, they still have all the knowledge and skills they gained from their classes, so they haven't lost anything by being ABD.