The two are factors of business environment.
Internal Environment refers to all the inlying forces and conditions present within the company, which can affect the company's working.The internal environment is company-specific and includes owners, workers, machines, materials etc.
External Environment is a set of all the exogenous forces that have the potential to affect the organization's performance, profitability, and functionality.The external environment is further divided into two components: micro & macro.
A business works in two environments: internal and external.
The internal environment defines all the interior forces of the company which might affect the working of the organisation. The internal environment consists of strengths and weaknesses of the organisation. On the other hand, external environments are the forces which can affect the organisation's functioning, profitability of the company. The external environment consists of opportunities and threats for the organisation. The nature of the internal environment is controllable and the nature of the external environment is uncontrollable.