Adobe Illustrator is an advanced vector-based software. So, unlike Photoshop’s pixel-based format, it uses mathematical constructs to create vector graphics.
In Illustrator, a line is composed of two dots connected by a computer algorithm, instead of just a line of pixels. Because of this, Illustrator is used often to create logos or anything that may need to be printed or displayed at different sizes.
A vector graphic will never lose its quality if it’s scaled up or down. Illustrator will also give you a better print output since it’s not resolution dependent. A drawback of Illustrator is that it can’t be used easily to modify images that are already created, since there are limited filters and image editing tools available to you.