A good way to understand resolution is thiking in the grid of pixels that you have on your screen, rows and columns. More lines, smooth curves, better images. Less lines, more "squares" on your image...
High Resolution is always relative. It s more like an ad than a default standard.
Whatever, in industry, usually 300 ppi (150 dpi) is a nice start resolution for a good printing.
Sounds funny, but video monitors, and computer screens use 72 dpi as default.
Usually, photography cameras offer higher resolution than the video/cinema high-resolution cams can do.
I guess you are looking for this chart:
http://www.design215.com/toolbox/megapixels.php
and a little bit more information:
http://www.design215.com/toolbox/print_guide.php
I hope this helps to clarify you.