Illustrator Vs. Photoshop
Vector: Vector graphics is the use of geometrical primitives such as points, lines,
curves, and shapes or polygon(s), which are all based upon mathematical equations to represent images in computer graphics. Drawing programs such as Adobe Illustrator use vector graphics.
Raster: Raster graphics or bitmap is the representation of images as an array of pixels, as it is typically used for the representation of photographic images. Photography programs such as Adobe Illustrator use raster graphics.
Pixel: (short for picture element, using the common abbreviation "pix" for "pictures") is a single point in a graphic image. Each such information element is not really a dot, nor a square, but an abstract sample.
There are instances when working with vector tools and formats is best practice, and instances when working with raster tools and formats is best practice.