Deixis is introduced to handle the 'orientational' features of language which are relative to the time and place of utterance.
(i) personal pronouns: I, you, he, etc.
(ii) adverbials of place and time: here, there; now, then
Deixis is merely the Greek word for 'pointing' or 'indicating'.
Lyons, John. 1968. Introduction to Theoretical Linguistics. Cambridge: Cambridge University Press.