What is Linguistics?
When people ask me what I do or did before I retired, and I say I am a linguist, I usually either receive a blank look or they ask how many languages I speak. When I reply that linguistics is the study of the nature of language, the blank look turns to puzzlement. Study language? Why?
Linguists do a lot of different things. At the heart of the field is the effort to describe languages - to specify what sounds they employ (phonetics), how these sounds combine to form meaningful units such as words (phonology and morphology), how words combine to form sentences (syntax), and how the meanings of sentences are formed from the meanings of the words that comprise them and, critically, of how these words are combined (semantics). Then there is the problem posed by the fact that we frequently use sentences to mean things that the sentences themselves don't mean. If I say Could you pass the salt? to you while we are eating together, I would normally mean for you to pass the salt to me even though that is plainly not what the sentence means. Understanding this phenomenon - how we use language in context - was and is my primary area of interest (pragmatics), and it includes, in my case, how we use language in advertising, politics, the law, as well as ordinary conversation.
Linguists do a great deal more than this. Those at the juncture of linguistics and psychology study how children learn language and how we process it. Historical linguists study how languages change and how they are related to each other. Dialectologists describe differences in the various dialects that make up a language. Sociolinguists study the social determinants of dialect differences. And there is more.
As for why someone would want to study linguistics, the answer is pretty clear: anything we can learn about humans -- especially about our higher cognitive functions -- is of intrinsic interest. And there are practical applications as well -- in the development of "natural" computer-human interactions, in understanding how advertisers bamboozle perfectly intelligent consumers through how they use language, in understanding the role of language in various areas of the law, and in understanding how we use language with each other in our daily lives.