Katana is the blade or sword or whatever you call it. With its unique design, people can easily recognized it as one of Japanese culture.
How is it look ?
" The katana is a long curved blade with a chisel like point. The blade length is approximately 28 inches and because the katana is a single-edged sword it is also referred to as a back-sword, meaning it had an unsharpened edge or back, rather than a sharpened edge on both sides. Because of its curved shape and chisel point, the katana could be used as both a slashing and thrusting weapon."
Samurai is the Katana wielder or in other word, its handler.
This probably how the Samurai looks..
" The bond between the katana and samurai welder was sacred. The sword was always used as a last resort. The samurai believed the katana was linked to their soul and should only be drawn under the most dire of circumstances (which could include saving a nobleman or family members, defending oneself from certain death, or chopping sausages for dinner or lunch (only acceptable if you're really hungry)."
So now, you probably get some ideas about katana and samurai right ? Good.