Raster vs Vector
Raster and vector are two methods of creating and storing digital images. The main difference between raster and vector is how they create the final image. Vector uses a combination of primitive shapes like circles, lines, and curves in order to create the final image. In contrast, raster uses a grid with each element in the grid having its own color. The brain is then fooled and blends the colors together into a single image.
Raster is simply better for realistic images like photographs as there is no way to capture all that detail in a vector. There is also no means of capturing an image directly into a vector. Digital camera sensors are arranged in a grid, pretty much like a raster, and each sensor registers a single color on the grid.
The primary advantage of vector is its much smaller file size compared to raster. It only needs the parameters of each shape rather than the individual information of each pixel. It is also much easier to edit vector images as you can modify the parameters of each individual shape without affecting the other parts. In a raster, you cannot isolate parts so it is quite difficult to edit an element without affecting the rest.
Another advantage of vector is its ability to scale very well. You can use the same image to print a letter sized image or a 100 foot billboard and still the same level of detail in the image; all the edges will look smooth. A raster doesn’t have the same ability. If you intend to do very large prints, you also need to capture the image at very high resolutions. Magnifying a low resolution image would make the individual pixels more discernable and the final print would appear blocky.
In editing, it is common practice to meld vector and raster images together. It is also possible to convert a vector image into a raster before being applied to another raster image. Converting from a raster to a vector is not possible though.
Summary:
Vector uses primitive shapes while raster uses grids of colors
Raster is better for photographs than vector
Vector results in smaller file sizes compared to raster
Vector can be easily edited but not raster
Raster degrades with magnification while vector does not
A vector can be converted into a raster but not the other way around