To you ladies, they're obviously part of your body, for better or worse. Sometimes you're proud of them, sometimes unhappy and most of you know how to use them to your advantage at least a little.
To us guys, however, your breasts are the object of something between strong interest and out-and-out obsession depending upon the guy (and the set). They make us fixate, double-take and lose our trains of thought.
They make our eye contact stray during conversation. They make us sigh involuntarily. They make us gawk.