An LLC (Limited Liability Company) is a business structure that provides legal protection but offers flexibility in how it's taxed. A single-member LLC is taxed like a sole proprietorship by default; a multi-member LLC is taxed like a partnership. LLCs can elect to be taxed as an S corporation or C corporation. The LLC itself doesn't pay federal income tax — profits and losses pass through to the owners. State fees and rules for LLCs vary.