What is Linguistics?

Linguistics is ...

Linguistics is the study of language - how it is put together and how it functions. Various building blocks of different types and sizes are combined to make up a language. Sounds are brought together and sometimes when this happens, they change their form and do interesting things. Words are arranged in a certain order, and sometimes the beginnings and endings of the words are changed to adjust the meaning. Then the meaning itself can be affected by the arrangement of words and by the knowledge of the speaker about what the hearer will understand. Linguistics is the study of all of this. There are various branches of linguistics which are given their own name, some of which are described below. Linguists are people who study linguistics.

Structures
Linguistic structures are pairings of meaning and form. Any particular pairing of meaning and form is a Saussurean sign. For instance, the meaning "cat" is represented worldwide with a wide variety of different sound patterns (in oral languages), movements of the hands and face (in sign languages), and written symbols (in written languages).

Linguists focusing on structure attempt to understand the rules regarding language use that native speakers know (not always consciously). All linguistic structures can be broken down into component parts that are combined according to (sub)conscious rules, over multiple levels of analysis. For instance, consider the structure of the word "tenth" on two different levels of analysis. On the level of internal word structure (known as morphology), the word "tenth" is made up of one linguistic form indicating a number and another form indicating ordinality. The rule governing the combination of these forms ensures that the ordinality marker "th" follows the number "ten." On the level of sound structure (known as phonology), structural analysis shows that the "n" sound in "tenth" is made differently from the "n" sound in "ten" spoken alone. Although most speakers of English are consciously aware of the rules governing internal structure of the word pieces of "tenth", they are less often aware of the rule governing its sound structure. Linguists focused on structure find and analyze rules such as these, which govern how native speakers use language.

Linguistics has many sub-fields concerned with particular aspects of linguistic structure. The theory that elucidates on these, as propounded by Noam Chomsky, is known as generative theory or universal grammar. These sub-fields range from those focused primarily on form to those focused primarily on meaning. They also run the gamut of level of analysis of language, from individual sounds, to words, to phrases, up to cultural discourse.
Sub-fields that focus on a structure-focused study of language:

Phonetics, the study of the physical properties of speech sound production and perception
Phonology, the study of sounds as abstract elements in the speaker's mind that distinguish meaning (phonemes)

Morphology, the study of morphemes, or the internal structures of words and how they can be modified

Syntax, the study of how words combine to form grammatical phrases and sentences

Semantics, the study of the meaning of words (lexical semantics) and fixed word combinations (phraseology), and how these combine to form the meanings of sentences

Pragmatics, the study of how utterances are used in communicative acts, and the role played by context and non-linguistic knowledge in the transmission of meaning

Discourse analysis, the analysis of language use in texts (spoken, written, or signed)

Stylistics, the study of linguistic factors (rhetoric, diction, stress) that place a discourse in context

Semiotics, the study of signs and sign processes (semiosis), indication, designation, likeness, analogy, metaphor, symbolism, signification, and communication.