It is possible for signs to have two kinds of meaning, referred to as indexical and referential. Indexical meaning is meaning that is context-dependent. For examples, consider the traditional deictic categories of person, place, and time. Some frequently-used English examples are pronouns, demonstratives, and tense markings. Referential meaning, also called ‘semantico-referential function’, is when a word functions to describe events or states of affairs in the world independent of the context of the utterance. An example of this could be
“A cat is on a mat.”
because the meaning that it conveys is independent of who says it, when they say it, etc.
A referential indexical, also called a ‘shifter’, is a sign which contains both referential and indexical meaning. So for example, the word ‘I’, as in
“I went to the store.”
is a referential indexical. It has referential content, in that it refers to the singular first person, and indexical content, in that its meaning depends on who uttered the word.
So, to restate this. There are two kinds of meaning. Meaning that changes depending on context (e.g. who “I” is, when “now” is), and meaning that stays the same no matter the context. The latter is the semantico-referential function; referential, because it references things in the world; semantico-, because it works based on semantics (intrinsic meaning) rather than pragmatics (contextual meaning).