There were two main version of the tank. (NOTE: these names were given to them by the germans for the Russian don't call them this for some Reason), The first one was the T-34/76, It was armed with the F-34 76mm Anit-Tank gun, and had upto 90mm of sloped armor. The second version was a resolet in the n,increasing number of tiger tanks, it was armed with a 85mm gun and was called the T-34/85. It had a little it more armor but was able to take on panthers and tigers now for it had a bigger stronger 85mm gun. This model is actually in some armies today. But of course only like malitias who can't get big modern tanks.
The was so good that the Germans thought the best way to destroy it was to copy it. And the Panzer V Medium Tank "Panther" apeared. It surelly was an equal in fire power and protection. But like all other German tanks it was hard to build in larg numbers. Unlike the T-34/85. Almost 50,000 were built before the war's end.
T-34/76: First production model. Armed with a 76mm gun, one of the best tanks of it's time.
T-34/85: An upgraded version of the T-34/76 but given a diffrent turret with a larger/stronger 85mm gun, plus some more armor.
T-34/100: An attempt to put an 100mm gun in the turret of the T-34/85.