In most cases, the meaning of a word is its use.

This statement is indicative of a shift by Wittgenstein away from his "picture theory" of language as expressed in the Tractatus Logico Philosophicus, which sees the world as a collection of facts which can be reliably expressed by means of language, to a more fluid theory of language expressed in the investigations. This view held that language depends on how you say something and the context in which it is said.

If language is to be a means of communication there must be agreement not only in definitions but also (queer as this may sound) in judgements.

In accordance to the context-dependent language theory expressed in investigations, Wittgenstein asserts that since no fact is provable, we must always seek agreement on facts as true before using them as basis for linguistic statements.

So in the end, when one is doing philosophy, one gets to the point where one would like just to emit an inarticulate sound.

This statement captures nicely Wittgenstein’s notorious tendency to work himself up into an orgy of frustration with the linguistic tangles of traditional philosophy. Making such a sound is an endeavor to find something objective, a statement that is not open to contestation, though even this sound takes its meaning from the context in which it is expressed.

We must do away with all explanation, and description alone must take its place.

For Wittgenstein, no single explanation or meaning is universal. Description is a more effective method of philosophy and will reveal how meaning is always subjective.

a nothing will serve just as well as a something about which nothing could be said.

To link back to the third quote, sometimes for Wittgenstein, saying nothing on a topic we don’t understand is better than saying something for the sake of it, since this avoids the confusion that comes in pursuing linguistic explanations.

"What is your aim in Philosophy?”
“To show the fly the way out of the fly-bottle”

Human beings love wrestling with problems and have developed a wealth of linguistic and logical methods to do so, as evidenced in traditional philosophy. For Wittgenstein, however, such pursuits, which are motivated by a desire for the honey of enlightenment, are counterproductive and can lead to thinkers trapping themselves in the circular glass prisons of their own heads.

If God had looked into our minds he would not have been able to see there whom we were speaking of.

Wittgenstein’s theory of mind was based on its unknowable nature. He rejected the notion that the mind could ever be understood by means of experimentation or observation, since the language we would use to describe what we see would simply not capture the experiential reality of mind.