Photoshop is raster-based and uses pixels to create images. Photoshop is designed for editing and creating photo or raster based art. When the program was created it was for photographers, but over time the program grew to help all kinds of artists do different kinds of work. Now Photoshop is known for its interface design, web pages, banner ads, video graphics, and the actual use of creating and editing images for printing.
Photoshop is capable of doing so much and is known for learning so easily that it is seen as a one stop shop but Photoshop is not the best program for all kinds of artwork and design.
Illustrator works off vectors, these are points used to create perfectly smooth lines. This program is for creating and editing vector-based work such as graphics, logos, and other design elements. Vectors are scalable images that can be sized as small or as large are you need them to be, but look the same when it comes to clarity and resolution.
Illustrator is not ideal for creating multi-page documents and using the program this way would create some drawbacks. Illustrator doesn’t have a way to setup master pages the way that InDesign does. This is a necessary tool when you’re building documents that use templates. Illustrator also doesn’t allow you to automate page numbers. This is another feature InDesign supports, which can be especially useful when dealing with larger documents.
Photoshop is a bad program to use when creating logos, it will do nothing but cost you time and money. Creating a logo in Photoshop cannot be enlarged or manipulated in the same manner that an Illustrator based logo can. Type will print clearest at vector-based rendering. The Adobe Creative Cloud Package has many different programs to create different art in separate practices.