Sole Proprietor is a business owned by one individual. This type of business is easy to create and can be often created just by engaging in commerce and not even establishing a formal organizational structure, but the individual is liable for all activities and lacks any corporate protections.
Being an owner and operator of a business can be the same person, or different persons. If an employee is hired to manage the business, and the owner does not participate in the management of the business, the owner is still liable for the actions of the employee.
The sole proprietor owns all assets and debts associated with the business. These debts or liabilities are unlimited, and is the sole responsibility of the owner under this structure. Debts or loans can be structured so to minimize the liabilities to the owner, but this is no longer a common occurrence.
This also means that all revenues are considered the personal revenue of the owner, and is taxed as that owners income.