Medieval armour

• Head armour: Great helm, made out of metal.
• Torso armour: Cuirass, made out of metal.
• Shin Guards: Greaves, made out of two metal plates and used leather straps to hold it onto your leg.

Japanese armour

• Head armour: Kabuto, made out of iron and leather plates that are riveted together. 
• Torso Armour: Dou, also made out of iron and leather, it has been made in little pieces that have been formed to make one chest armour. 
• Shin guards: Suneate, made by iron splints, it is connected together with chainmail. 

What was different between the two armour?

The difference between Medieval Armour and Japanese Armour is that armour from the Medieval time are usually made by metal and steel. Japanese armour on the other hand are made by iron and leather most of the time and had a few that were made by metal. Japanese head armour was actually very different from medieval head armour because medieval head armour is plain and the Japanese head armour have a "scary" mask on top of it to intimidate the enemy.

http://en.wikipedia.org/wiki/Japanese_armour
http://en.wikipedia.org/wiki/Greave
Other references about Medieval Armour are on the Timeline page.