Here is a great explanation:
Q: Why can't I use a blender or food processor instead of a juicer? I'm thinking about buying a juicer but I'm not sure I need one.
A: A blender will not extract the fiber/pulp from the juice. It will mash the produce to liquify it, but will not take it out. Seperating the fiber from the juice allows your body to digest and soak in all of those live vitamins quicker. It's also more concentrated.
Blending 3 apples vs. juicing three apples is very different. Juicing the apples makes a super concentrated life giving liquid that your body can assimilate quickly.
Getting a cheap juicer is better then no juicer at all.
If you're still thinking about getting a juicer, make sure you go to the Review Juicers page to start researching a few.
Here is a link to the site with lots of valuable information: