A good way to understand resolution is thikingthinking in terms of the grid of pixels that you have on your screen, rows and columns. More More lines, smooth curves, better images. Less Less lines, more "squares" on your image...
High Resolution is always relative. It s It's more like an adof a recommendation than a default standard.
Whatever, in industry For instance, usually 300 ppi (150 dpi) is a nice startphotography cameras offer higher resolution for a good printing.
Sounds funny, butthan the video/cinema high-resolution have. Video monitors, and computer screens use 7296 dpi asby default.
Usually For printing, photography cameras offer higher300 dpi is a good starting 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 These resources should be helpful:
http://www.design215.com/toolbox/print_guide.php
I hope this helps to clarify you.