Instead of producing something common to all that we call language, I am saying that these phenomena have no one thing in common which makes us use the same word for all,--but that they are related to one another in many different ways. And it is because of this relationship, or these relationships, that we call them all "language".
Consider for example the proceedings that we call "games". I mean board-games, card-games, ball-games, Olympic games, and so on. What is common to them all? ... If you look at them you will not see something that is common to all, but similarities, relationships, and a whole series of them at that.
I can think of no better expression to characterize these similarities than "family resemblences".
Ludwig Wittgenstein, Philosophical Investigations, Translated by G.E.M. Anscombe, Basil Blackwell, 1958. Excerpts taken from sections 65, 66, and 67.
Wittgenstein further defines his unique term "Sprachspiel" (usually translated as "language-game") in section 7 of his famous "Untersuchungen" ("Investigations"). First, though, let's look at section 2. Wittgenstein here describes a language that serves as communication between two builders, A and his assistant B. There are multiple types of building-stones that A might request B to bring to him. The two have devises a language consisting of these words: "block", "pillar", "slab", and "beam". Wittgenstein writes, "A calls them out;--B brings the stone which he has learnt to bring at such-and-such a call.----Conceive this as a complete primitive language" (Section 2).
In section 7, Wittgenstein defines the term "Sprachspiel" in reference to the complete primitive language described in section 2. He urges us to think of the processes in 2 as akin to those used to teach children their native language. Wittgenstein defines his term: "I will call these games 'language-games' and will sometimes speak of a primitive language as a language-game. And the processes of naming the stones and of repeating words after someone might also be called language-games. Think of much of the use of words in games like ring-a-ring-a-roses. I shall also call the whole, conssisting of language and the actions into which it is woven, the "language-game" (Section 7).
Wittgenstein's term, which we must remember is his own, is then meant to refer to primitive language processes. As Wittgenstein will show through the Philosophical Investigations there is a sense in which all language is of this sort, that is all language can be conceived on the language-game model Wittgenstein describes (the model itself is almost completely flexible). There is, Wittgenstein thinks, no reasons other than practical ones to make certain distinctions in language. One common distinction we make is between meaningful and nonmeaningful language. Through his notion of meaning as use Wittgenstein tries to show that this distinction is not one rooted in the metaphysical structure of language nor in the ontic presence of a system of signification, rather it is rooted in the actual practice and use of our human language-games.