In language, text is something that contains words to express something. The term usually has broader meaning.
In linguistics text enters at least two types of contrasts. One is that between system and text, system being understood as the ability of the speakers to communicate using verbal signs, and text being understood as the product of this ability. The other is between text, understood as written text, and speech, spoken text.
In literary theory a text is the object being studied, whether it be a novel, a poem, a film, an advertisement, or anything else with a linguistic component. The term came into use with the rise of cultural studies, and the corresponding broadening of what it was one could talk about when talking about literature.