The philosophy of language is one of those niche areas of philosophy that you don't hear much about in the mainstream amidst all the more popular "I think therefore I am" stuff. There's probably a reason for that - language philosophy tends to be the kind of dry, analytical field that deconstructs stuff you already had figured out before you were able to walk.
Think for a moment about the concept of the proper noun, that special kind of noun that begins with a capital letter and serves to name some particular thing, like David, Chicago or Wednesday. As opposed to regular nouns like 'cat,' which refer to a category of things, proper nouns single out and identify some singular, independent thing of which only one exists. You've had that particular concept mastered since you were about two years old, but philosophers (not quite as wise as two-year-olds) have been puzzling over it for centuries.
Consider the word Istanbul. You know what I mean when I'm talking about Istanbul, it's a city in Turkey. According to usually-good-enough common sense, the concept of Istanbul is synonymous with that actual city. I am not talking about just any city. I'm not talking about Batman. I'm talking about the one and only Istanbul. But it turns out that (of course) there is a gigantic philosophical problem with this theory, a problem so huge that people have lived and died dedicating their entire lives to trying to untangle it. The problem is that, according to that old ragtime tune, Istanbul is Constantinople.
Here's why this fact is like a giant turd in philosophy's apple juice: "Istanbul is Constantinople" is an informative statement. If you didn't know that Istanbul and Constantinople (and worse, Byzantium as well) are all the same city, then you've learned something new. On the other hand, if I say "Istanbul is Istanbul," then you're really not learning anything at all. "Istanbul is Istanbul" would never have made it to the Billboard magazine charts, nor would it have been more popularly covered by They Might Be Giants in the early 90s, because it's a completely meaningless sentence. (In that sense, perhaps it could have been pulled off by R.E.M. or Fall Out Boy). But if you look at this through the annoyingly mathematical lens of analytic philosophy, you'll find we have somewhat of a paradox:
If X = Istanbul, Y = Constantinople, and Z = the actual city to which both names refer, then:
X = Z
Y = Z
and
X = Y
...are all synonymous statements. They're all self-evident, all mean exactly the same thing. Problem is, go back to:
Istanbul = Constantinople
Istanbul = Istanbul
...and suddenly we have two statements that mean two different things. Saying that Istanbul is Constantinople is not the same as saying that Istanbul is Istanbul, because one is meaningful and the other is not. So neither the word Istanbul nor the word Constantinople can directly refer to and be synonymous with the common thing that we are trying to identify. While most of us shrug and say "we can deal with this," philosophers scream to the heavens and demand we have a philosophy that can decode this mystery.
So what is the real relationship between the word Istanbul and the city we're calling Istanbul? What is going on in your brain when you read the word Istanbul and envision a bunch of minarets and turbans and half-moons and awful candy? There are two main theories:
Descriptivism argues that a name is a shorthand for a description. It's a way of zipping up a whole lot of data in a small amount of space. This is the solution Gottlob Frege came up with so that he could manage to sleep at night. It makes sense because most of the statements we actually make in our day to day lives are descriptive ones. Whenever we say that "the sky is blue" or "Natasha forgot to wear pants again today," we are describing the world around us. A descriptivist like Frege would argue that, when we say "Istanbul," we are actually saying "the largest city in Turkey." Likewise, when we say "Turkey," we're actually saying "the Asian country that is bordered by Greece, Bulgaria, Georgia, Armenia, Iran, Iraq, Syria and Azerbaijan." And when we say "Greece, Bulgaria, Georgia, Armenia..." Look, you get the picture. According to Frege, a name is like a website that you save in your favourites folder so that you don't have to type in the full web address every time. He didn't use that exact analogy because he died in 1925, but I think he would have endorsed it.
"But wait," you might be saying, "that still doesn't solve the problem! Gottlob Frege wasted his life and had a silly name!" Well, you're right, but he did try to address this. According to Frege, the words Istanbul and Constantinople are describing identical things, but they differ in terms of the "sense" or context in which they're being used. While Istanbul refers to the city since its Arabic conquest, Constantinople refers to the same city before that time but after Byzantium was overthrown by the Romans. While we're describing the same physical location, the words remain unique in terms of the sense in which they are used.
If this all sounds pretty rock-solid and intuitive, then you are clearly new to philosophy, because (as always) someone came along to throw a flaming poop-covered cinderblock through the window of this philosophy party. His name is Saul Kripke, and he thinks descriptivism is absolute garbage. Here's why:
Consider the name Shakespeare. If we're working with descriptivism, then when we say Shakespeare, we're really saying the guy who wrote Hamlet, Macbeth and Othello or whatever your favourite Shakespearean play is, Henry the Seventeenth or whatever. That's how we know Shakespeare today, and if you ask anybody who "Shakespeare" was, they're likely to give you a funny look before they rattle off this description - "Shakespeare was this and that and he lived whenever and he wrote this and the other thing."
There is, however, a popular conspiracy theory about Shakespeare. Roland Emmerich is making a movie about it that will probably make him another billion blood-dollars. The theory goes that Shakespeare did not actually write the plays that we attribute to him. One of the more popular alternative theories (the "Baconian Theory") states that Shakespeare's plays were actually written by Kevin Bacon.