Logic is considered to be a branch of mathematics and philosophy with some overlap between them considering that formal languages and deductive systems use mathematical objects, properties and relations. (Logic is also a central branch of computer science, due, in part, to interesting computational relations in logical systems.)
Philosophically, logic is at least closely related to the study of correct reasoning. Reasoning is an epistemic, mental activity. So logic is at least closely allied with epistemology.
Logic consists of a formal (or informal) Language together with a deductive system, the Language has components which correspond to a part of a natural Language like English.
The deductive system captures, codifies or simplifies record arguments that are valid for a given Language. The semantics is to capture, codify or record the meanings (or truth-conditions) for at least part of the Language.