and; as well as~
A formal conjunction meaning 'and' or 'as well as', used to join nouns in written and official language.
及び is a formal, written-language equivalent of と or や. It joins nouns or noun phrases, not clauses. You will see it in legal documents, contracts, academic papers, news reports, and official notices. In speech, it sounds stiff and unnatural; use と instead. Note that 及び is a conjunction, so no particle is needed before or after it—just place it between the nouns. It can also be used to list multiple items, where it typically appears before the final item.