What is the difference between eyeshadow primer and concealer?

I was just wondering if you could use normal concealer or just even cover up as an eye primer instead of paying big bucks for an actual eye primer?What is the difference between eyeshadow primer and concealer?
Concealer works great as an eyeshadow primer substitute, but if you want it to last longer, than use eyeshadow primer.





I use concealer as my ';primer.'; It only lasts for about 8 hours though, but I'm okay with that, because I don't need to be with make-up for 8 hours. :)