Alpha channel

The hidden channel that says how transparent each pixel is. The reason an image can sit cleanly on anything.

Alpha is the fourth answer every pixel can give: besides how red, green and blue, also how present. Full, absent, or the crucial in-between, translucency, which is what lets an edge dissolve gracefully into whatever lies beneath instead of ending in a jagged cliff.

The reason an image can sit cleanly on anything, and the first thing to check when one cannot: a logo arriving with a baked white background instead of alpha is the classic handoff failure. Formats matter, PNG and WebP carry alpha, JPEG cannot, and half-transparent edges must be exported against the tone they will actually sit on, or they arrive haloed.