Against the background that a definition in neuroscience (or philosophy) usually cannot be as exact as, e.g., in mathematics, there may be several starting points to find a (not THE) answer for your question:
cognition refers to the exercise of our basic intellectual functions in service of a mental goal. Cognition is usually viewed in terms of computational functions performed on information delivered either to our senses from the perceptual world, or through memory. Cognition includes an array of basic cognitive processes including perceptual processing, short term memory, long term memory encoding and retrieval, decision making, planning, reasoning, and language. It also includes the translation of thought to action.
Cognition is the process by which the sensory input is transformed, reduced, elaborated, stored, recovered, and used. Please study theory of social cognition/ social cognitive theory. It will help your understanding.