hi jen,
...i just posted this response in the other post you replied to, so have copied here below:
illustrator is a vector package and is predominantly used in the graphics world for logos, t shirt designs, large format graphics, anything that is needing scalable graphics without loss of quality.
photoshop is bitmap based program, meaning you need to specify a resolution suitable for the end purpose, not really recommended to be designing logos in photoshop, but having said that, photoshop has it's place for sprucing up vector artwork in some instances. You just have to aware of the resolution your dealing with...
...photoshop does have vector drawing features, but to maintain that vector (like fonts, without faux styles) you have to save to Photoshop PDF, but the downside is the PDF files from photoshop can be bloated in my experience. I've found it better to print from photoshop through the Adobe PDF Printer to get smaller PDF files that maintain vector shapes and embedded fonts...
...if scaling up bitmap graphics in page layout programs you lose resolution...
...1bit black and white images (known as bitmap mode) need to be 600 to 1400dpi at actual size...
...continuous tone RGB, CMYK and greyscale (like magazine printing) need to be 300dpi at actual size, but can be lower if dealing with large format printing (in many cases you can use 100dpi at actual size or less)...
...but for logos on large (or small) format printing you really need to use a vector format logo for optimum quality...
...illustrator is also a bitmap program to a degree in that you can use transparency effects, similar to photoshop. With illustrator you also have to be aware of resolution when using bitmap effects (like drop shadows, feathers etc) or importing images. This is controlled under the effect menu (effect > document raster effects settings) and also by the transparency flattening on output to postscript or PDF version 1.3...
...there is much you can do in illustrator that you can't do in photoshop and vice versa, indesign is a bit like illustrator with some features, so all threes programs kind of cross over to a point...
...all in all though, logos really need to be created in a vector program, all the best logos in the world are vector based drawing, simply because vector allows greater flexibility in the creation process, without the worry of resolution problems. As indesign is also vector based people do create logos with that program too because it has some of the features illustrator does...
andrew