As a linguist, you do not need to know or learn many languages; rather you learn about language. Linguistics is the scientific study of human language, its structure, its history, its acquisition and its use in communication.
Theoretical linguists study commonalities and differences between languages and they develop descriptions of the structure of individual languages, e.g. English. The study of theoretical linguistics breaks down into the following areas:
Phonetics and Phonology - the study of speech sounds and their rules
Morphology - the study of word formation and word structure
Syntax - the study of sentence structure
Semantics - the study of meaning
Pragmatics - the study of language use
In addition, there are many areas of linguistics that deal with development and use of language. For instance, linguists study how languages are acquired, how they change over time, and how they are used in real-time production and comprehension or among different social or ethnic groups of speakers. These questions are addressed in the following areas of linguistics:
Historical Linguistics - the history and development of language
Sociolinguistics - the use of language in social contexts
Psycholinguistics - the processing of language in real time production and comprehension
Neurolinguistics - how language is represented in the brain
Language Acquisition and Bilingualism - the acquisition of language(s) in children and adults
Anthropological Linguistics - the use of languages in different ethnic contexts
Dialectology - the study of language-internal variation
Computational Linguistics -language as a formal algorithm
Linguistics intersects with many other disciplines in the humanities, the social and the natural sciences that study particular aspects of language, for instance, Philosophy, Psychology, Literature, Language Teaching and Pedagogy, Sociology, Biology, Computer Science, and the Health Sciences.
By studying linguistics, you discover intriguing facts about language which will be useful for language learning, language teaching and communication. Plus, linguistics is fun!