'I think therefore I am' - Descarte
'Cogito ergo sum' is the famous central tenet of Rene Descarte's dualistic view of life. In English it translates to mean 'I think therefore I am'.
'Cognition' is the quality of the mind including thought, memory, consciousness, beliefs, perceptions, reasoning etc.
In short Cognition is about thought.
'Behaviour' is pretty self explanatory as the things we do, except that in CBT the concept of 'behaviour' may also include emotions as things we do.
'Therapy' is about reconnecting, healing and growing.