There are two distinct LLCs: Single member or multiple members, both which can be taxed as all three previously mentioned entities (sole proprietorships, partnerships, corporations). However, they need to file different forms to be eligible.
Single member LLCs need to file Form 2553 to be taxed as an S corporation, or Form 8832 to be taxed as a corporation. By default, single member LLCs are taxed as disregarded entities: if the single member is an individual, it is further taxed as a sole proprietorship, but if it is a business entity, then it is taxed as a division of the corporation.
It is important to remember that for federal tax purposes, employment taxes, and some excise taxes, single member entities that do not elect corporate status will still be treated as separate entities.
On the other hand, multiple members LLC must file Form 8832 to be taxed as a corporation and Form 2553 to be taxed as an S corporation if they qualify just like a single member LLC. However, by default, multiple members LLC are taxed as a partnership.