Vector graphics

Vector graphics is the use of geometrical primitives such as points, lines, curves, and shapes or polygons—all of which are based on mathematical expressions—to represent images in computer graphics.
Vector graphics are based on vectors (also called paths or strokes), which lead through locations called control points or nodes.
Each of these points has a definite position on the x and y axes of the work plane and determines the direction of the path; further, each path may be assigned a stroke color, shape, thickness, and fill.
These properties don't increase the size of vector graphics files in a substantial manner, as all information resides in the document's structure, which describes solely how the vector should be drawn.

substantial :
実体がある、実在する
がっしりした、頑丈な
〔食事が〕十分な、栄養がある
〔数量・程度などが〕かなりの、相当な