An ELT Glossary : Anaphoric, Cataphoric and Exophoric Reference
Anaphoric reference : An item in the text forms a cohesive link with another item which has already occurred - ie it refers back to and replaces that item, thus avoiding the need for repetition. Eg: a) in I bought a new car yesterday. It was a real bargain. "It" refers back to/replaces "a new car"; b) in Did you see the book which I left for you? "which" refers back to/replaces "the book"
Cataphoric reference : An item in the text forms a cohesive link with another item which occurs later - ie it refers forward to that item. Eg : given that the following is the beginning of the text - I walked around the corner and stopped dead. It was the biggest dog I'd ever seen. - then "It" refer's forward to "the dog".
Exophoric reference : An item in the text refers to something completely outside the text but understandable from the context. Eg Can you give me those books. NB: Exophoric reference is not a matter of cohesion, as the referring item links to something outside the text.
Anaphoric and cataphoric reference can be practised in the classroom by gapping a text and taking out all of the referring items, then asking the students to replace them.
See also : deixis, reference and substitution