For me, being attached means that T and I have a close bond. And we can often connect with each other in quite an intimate way. I trust him. He "gets me" and that makes us even closer. We know each other so well that we can talk in a kind of shorthand. All this makes me feel attached. It's actually a great feeling, very warm and comforting and secure.
You know how little ducklings will imprint on whatever walks by them during a critical time after they hatch? And then they follow that animal (usually the mama duck) or object anywhere? I kind of feel like that with my T, that I am imprinted to him, and maybe that is part of the attachment. There almost feels something biological about it all.