A drawing described by curves
A vector image is closer to a set of drawing instructions than a tiny mosaic. Its file can describe a line by its endpoints and a curve by control points that determine its shape. A circle, for example, can be stored as a geometric path, along with information about its stroke and fill.
Because those instructions describe relationships and proportions, enlarging the image does not stretch a fixed set of colored squares. The software recalculates where the paths should fall at the new size. A curve that spans a few millimeters on a screen can be redrawn to span a billboard while keeping the same smooth outline.
The screen still uses pixels
A monitor or printer ultimately needs a grid of dots to show the image. The graphics software converts the paths into that grid—a process called rasterization—and can do it again at the output’s resolution. At a small size, it may use partial shading along an edge so the boundary looks smooth rather than jagged.
That makes vectors especially useful for logos, diagrams, and lettering, which often need to appear at many sizes. It does not mean every image can be enlarged without a change in appearance: a vector illustration contains only the shapes and detail its creator put into it. But its outlines do not become blocky merely because the image is scaled up.
