>>11535480oops forgot to respond to this one. there's a lot to say about this, but i'll try to keep it short: for most of history, grammarians have mostly been interested in the question "in a given language, what are the grammatically correct expressions and their meanings?" but these days, linguists want to ask questions like "what are the reasons (genetically inherent, environmental, or otherwise) why all human languages have the grammatical and ungrammatical expressions that they do, with the meanings that they have?"
let me demonstrate with an example: any English grammarian before 1950 could have told you that (1) is fine, but they definitely would not have come up with a sentence like (2), which turns out to be wrong, but for interesting reasons. And it turns out that to explain cases like (2) in anything resembling a principled way you need to develop a somewhat detailed theory of what kind of structures are used in human language. (If you're curious about this example, google "adjunct island constraint")
(1) Which movie did John say Bill saw?
(2) * Which movie did John have dinner before Bill saw?
now back to your question: the most high-minded in the field like Chomsky say that linguists are ultimately cognitive scientists and want to develop an empirical understanding of that part of the brain/mind that is responsible for human language--the scope of its responsibilities, its architecture, its interfaces with the rest of the brain/mind, etc.
Linguistics is an incredibly motley field though, containing people who would describe themselves as anything from an anthropologist to a computer scientist to a logician. A lot of linguists would grate at Chomsky's research statement and just say that they're interested in describing human languages in less rarefied, less remote terms.
