An LLC is a legal form of company that provides limited liability to its owners in the vast majority of United States jurisdictions. LLC's do not need to be organized for profit. LLC's are quickly becoming the most popular form of business because of it's ease and flexibility.
A corporation is a separate and distinct entity under the law. The corporate business structure can help shield the business's owners–the corporation's shareholders–from liability and, under some circumstances, help them reduce their taxes.
A power of attorney (POA) or letter of attorney is a written authorization to represent or act on another's behalf in private affairs, business, or some other legal matter. The person authorizing the other to act is the principal, grantor, or donor (of the power)