Employees in BQE CORE are people working within your company. These people are on your payroll and can be part-time or full-time employees.
'Vendor' is a broader term that can be used for contract employees, outside consultants, subcontractors, suppliers, or any outsourced persons who provide services (or products) for which you owe them money. Though they may be able to enter time and expenses in CORE, they are not on your company's payroll.
Vendors and outside consultants are practically the same in regards to what they do and actions they can perform in CORE. Vendors are usually companies hired to do work for your projects, whereas outside consultants are individuals. Neither of them are on your company's payroll, but they both can enter time and expenses in CORE with the right security permissions and subscriptions.
An independent contractor is a person contracted to perform work, but they can control how to do their work. The employer is interested only in the contract employee's results and they typically work unsupervised. Independent contractors must pay their own Social Security and Medicare taxes.
Generally, a worker who performs services for you is your employee if you have the right to control what will be done and how it will be done. Generally, people who do business for themselves aren't employees. For example, doctors, lawyers, veterinarians, and others in an independent trade in which they offer their services to the public are usually not employees. However, if the business is incorporated, corporate officers who work in the business are employees of the corporation.
An employer may pay an independent contractor and an employee for the same or similar work, but there are important legal differences between the two. For the employee, the employer withholds income taxes, Social Security, and Medicare from wages paid. For the independent contractor, the employer does not withhold taxes.