High-key Lighting
A lighting approach in which most tones sit in the upper half of the range, with few dark shadows and a bright background.
In depth
High key is not simply overexposure: the subject is correctly exposed while the fill is raised to a near 1:1 ratio and the background pushed one to two stops above it, so the result is light and airy without losing detail. It reads as clean, optimistic and commercial, which is why it dominates catalogue and beauty work.
Examples in practice
A model in white against a white backdrop lit two stops above the key produces a shadowless, luminous frame.