The three practiced together upon one object is sanyamah or constraint.
Concentration (Dhaaranaa), meditation (Dhyaana) and cognitive absorption (Samaadhi) is one continuous process and when focused on a single focus of attention (the object), the three become know as sanyamah or constraint. Sanyamah is a constraint that gives rise to a very deep communion with the object. This constraint not only gives rise to the direct knowledge of the object but also to psychic powers (Siddhis) due to the total absorption of the mind which is a far cry from its usual preoccupations with external and internal distractions.
Another term for Sanyamah is integration. The whole science of Yoga is to produce an integrated being, to become the Self, the Seer instead of a collection of unintegrated selves that will disintegrate upon the passing of time and of life as we know it.