Well, I won’t claim to be a Buddhist scholar, but as I understand it attachment, and its converse aversion, describe relationships with things, people, ideas, etc that make us have a vested interest in preserving or clinging to things or in avoiding things. And the idea is that these feelings can create suffering. On a simple level, if I have an attachment to my morning cup of coffee, I will feel disappointement, anger, whatever if I miss it one morning. The suffering is not caused by the absence of the coffee, but by my attachment to it and my reaction to its absence. Likewise, if I am trying to read and someone keeps talking to me, my aversion to their conversation and my attachment to my book are the real cause of my suffering. If I didn’t feel I would be happier reading than talking to the person, than I wouldn’t. On a bigger scale, the same logic can apply to attachment to our family or our lives and aversion to more significant kinds of pain like illness or lonliness.
So yes, one aspect of the Buddhist approach to happiness is reducing attachment and aversion. Seeing things and people and feelings and acknowledging them, accepting them, but neither trying to cling to them or push them away. The core of the approach is the Noble Eightfold Path, which is much more detailed, and of course there are probably thousands of details and nuances missing.
All-in-all, an interesting idea. I’ve found it somewhat helpful to think about my own attitudes as the cause of my unhappiness, in terms of reducing my pointless suffering over minor things. I can’t say, though, that I’m any less attached to being alive or to the welfare of my family than I was before I discovered the idea, and I’m not sure the approach is without flaws or problems. Still, I think there’s a lot of value in it. If you’re looking for more to read, my fav orite Buddhist author is Thich Nhat Hanh, a Vietnamese monk who writes short little books of what you might call applied Buddhist psychology. Not scholarly stuff, by any means, but enjoyable.