These three terms are explained below.
Anaphora is a back ward reference.
Ex: I gave a banana to the monkey which it ate.
Here "it" refers back to the monkey and denotes an anaphoric relation
between it and monkey.
When the reference is a forward one it is called a cataphora.
Ex: If you want them, there are cookies in the kitchen.
Here, the actual thing that is pointed by "them" comes later
in the sentence. However, some linguists use anaphora to mean both
anaphora and cataphora as described by the above examples.
co-reference is where two or more instances of a name (or any seqeunce of symbols)
refer to the same real world entity. For example, one sentence may say
Prime minister X ... where as another sentence may say Mr. X .... If these two
instances refer to the same real world person, then they are said to be in
a co-reference relation.
