In Reason, Truth and History, Putnam talks about 'meaning' and 'reference', but I don't understand the difference between the two for him. He says:
what goes on inside our head does not determine what we mean.
What does that mean?
The difference is essentially the same as that which Gottlob Frege discusses in his seminal work On Sense and Reference. Putnam essentially uses the word meaning in place of Frege's sense, presumably because it seemed more intuitive for Putnam to splinter reference from meaning rather than make meaning a redundant term in our language.
The distinction between meaning and reference is simple: meaning/sense is the intension or the word, name or symbolic representation of an object; the reference is the thing to which the intension corresponds in the world—the reference is the object to which you are referring, if you will.
For instance, if you think of a battery, you have the word battery and you have symbols for batteries, such as:
and yet you also have the battery as a physical object, as an actual battery in the world, an extension. You have that which you mean and your ways of meaning it. The referent and the symbol to refer to it. An interesting parallel between analytic and continental philosophy is Frege's distinction between sense and reference, which is also acknowledged in semiotics as the distinction between signifier and signified.
Putnam differs from Frege in where meaning and reference sit. For Frege and others like him, meaning is a social, communicable sign/symbol and reference is in the world. For Putnam, both meaning and reference are in the world, because reference influences the formation of the symbols and names we use for meaning. Putnam sought to prove his argument with his famous Twin Earth thought experiment.
See this set of lecture notes for a nice summary of Putnam's views.