Pure detache is a form of bowing in which you play non-accented even notes. In order to achieve a good detache you need to train your finger tips to be flexible and to follow the hand in the same way as a paint brush flows on a surface. Practice changing bow direction while hearing as little of the bow change as possible.
Detache sec is a strong accented bowing. Petit detache is a short accented bowing usually played at the tip. Grand detache is a strong and full, long accented bowing. Detache simply means detached.