Context is the denotion of all elements defining the interpretation of communicated Content.
Context (lat. contextus = interweaved) denotes the surrounding of a symbol (concept) in an expression respectively its relationship with surrounding expressions (concepts) and further related elements.
Contexts denotes all elements of any sort of communication that define the interpretation of the communicated Content, as e.g.:
general contexts: place, time, interrelation of action in a message
personal or social contexts relation between sender and receiver of a message
Of course, these Relations determine how the information has to be interpreted, i.e. how the Semantics is really meant.
Context is important to make sense of Semantics and to determine the meaning.