What is the difference between whiteheads and blackheads?

Blackheads are a state where the pores are open and sebum oxidizes upon contact with air, turning dark (open comedones). In contrast, whiteheads are a state where the pore openings are blocked, preventing sebum from being expelled and appearing white (closed comedones). Both share the commonality of poor sebum discharge, but they are distinguished by whether the pores are open or closed.