Detachment is the antithesis of attachment.
It is the ability to let go. To surrender To let life and the universe follow its course freely. It is the ability to flow with reality instead of going against the current. It is knowing how to accept the things that you can not change and let them go.
Not saying, far from it, that you stop fighting. On the contrary, you have to keep giving everything, at all times. You have to continue pursuing your goals and your dreams. You have to work hard for what you want, and you should never give up your projects and dreams.
But you must be able to do it without getting attached, without clinging, without obsessing, without becoming addicted and, of course, without suffering.