Whats the career differences between 'Product Design' and Graphic Design?

I want to take occupational cles at college for design. But i dont know what the difference between these two are. What would i be doing as a career if i went into either of these fields? Is it stable? I like to draw more, but i wouldnt mind using a computer to make graphics. I aspire to make designs for tshirts, but i hear that is not the most stable choice. So what other choices of jobs would i have if i had a certificate in graphic or product design?