Vector icons are graphics that can be resized without losing any quality. They can scale to as large as you want or as small as long as they are clearly read. This is a popular format for logos and graphics that may need to be resized on a regular basis.
Icons that are vectorized can also be used on website. They communicate well with audiences and can be used with sections of text to enhance what it is you are attempting to communicate. Another feature of vector artwork is they load quickly on a website. Sometimes images can be large and take time to download. Using vector icons instead can increase the speed of your website download times.
Besides they look great when used properly with large groups of text and images.