The main difference between vector and raster format is how the data is stored. Vector formats store image information as a series of points, curves, and colors as mathematical data; raster format stores pixel data and has to save information about the color of every pixel in the image. The raster format has two main disadvantages:
Image size: Pixel-by-pixel data is a lot of information to store, and can really start to stack up on high-quality images.
Image quality: When you resize a raster image, the data doesn't scale well; if you shrink it, you lose pixel data as larger areas merge into smaller ones. If you enlarge it, you end up with a jagged image as single-pixel data has to expand to fill multiple pixels via messy interpolation.
Image size: Pixel-by-pixel data is a lot of information to store, and can really start to stack up on high-quality images.
Image quality: When you resize a raster image, the data doesn't scale well; if you shrink it, you lose pixel data as larger areas merge into smaller ones. If you enlarge it, you end up with a jagged image as single-pixel data has to expand to fill multiple pixels via messy interpolation.