A speech therapist not only works on teaching speech sounds (known as phonology - those stubborn R's!), but also language. Language encompasses two areas: receptive and expressive. Receptive language is what your child understands. This can include following directions, pointing to pictures that are named in a book, or answering questions. Expressive language is what your child says (or communicates through other means, such as a speech output device, sign language, etc.).
Language includes the following areas: semantics (word meanings or vocabulary), morphology (units of meaning, such as word endings, plurals), syntax (sentence structure, which is word order and different types of sentences), and pragmatics (social language -- such as maintaining a topic, using and reading body language, answering questions, clarifying).
If you have any questions or concerns about your child's speech and language development, please do not hesitate to contact your child's teacher or myself!