Spot (Color Field)
An independent visual unit defined purely by color or material, without an outlined edge of its own.
In practice
In this sense, a spot is an area that holds together because its color or material differs from its surroundings, not because a line encloses it: a patch of yellow on a gray wall, or a cork inset in a white tabletop. Designers use such fields to group content without borders, as when an app card is simply a lighter rectangle on a darker page. Print production uses spot color differently, for a premixed ink.
Often confused with spot color
Here a spot is a shape defined by color alone; in printing, a spot color is a specific premixed ink, such as a brand's exact orange.
Try this
Lay out three labels on a page, first with outlines, then as colored patches without lines, and see which groups more clearly.