Illustrations in general is a decoration, interpretation or visualisation of a text, concept or process. Illustrations are mostly used for print or digital published media. Common examples are posters, flyers, magazines, books, educational materials, animations, video games, films and so on.
Vector illustrations, better known as vector graphics, are computer graphic images that are connected by lines and curves to create polygons and other shapes.
Vector graphics have the unique advantage over raster graphics in that the points, lines, and curves may be scaled up or down to any resolution with no aliasing.
Common uses of vector illustrations are logo designs, web design, animations, and so on.