Wittgenstein tell us that a word's meaning is NOT derived from its letters, nor connected to some object that it might signify. Some words obviously do not have "things" which they are directly connected to, such as very, there or this, while some words stand for different things at different times, such as the word "bad", or "fat" or numbers. Instead, words are connected to meaning by the structure they exist in and not by some property intrinsic to the word itself. Furthermore, words do not exist as a creation, or an idea within the speaker. I think "dog" when I say dog, so "dog" means dog. This too is incorrect, because a word's meaning is only valid within a system, and just because I want "dog" to mean dog and not cat, I have either to operate within a language system, or change the system enough that it adapts to the new meaning placed upon within it. Furthermore, a particular definition may work with one set of users but not for the entire set; there may be multiple language systems at play. Therefore, a definition of a word is never fixed and cannot be limited or solidified. Instead a true definition is only the field of possible definitions within a system. Some being more useful within the larger system than others.
Accordingly a "theory" of language, much like a rigid definition, is useless in explaining language's terms and concepts because it is a prescription, a predetermination of the future. However, Wittgenstein reminds us that in language, like in chess, the act itself is not important but what happens before and after that is.