Yukatas are the light, summer kimono typicaly 
seen in anime worn at festivals. They ae made out 
of cotton, generally, and a heck of a lot less 
formal. They don't rquire all of the layers that 
a forml kimono does. A real kimono is generally 
made out of silk or some other high quality (and 
usually expensive) material. The patterns can be 
sewn onto the higher quality kimonos (yukatas are 
just prints)...generally, it's like "casual 
dressy" and "dressy dressy".

-Misha