User blog comment:Deshiba/Solo Queue: Skewed perceptions./@comment-3466579-20130730184113

If you think about the tank's role you cannot miss the fact that having a lot of health and defenses does not make you a tank, since enemies can just focus on other target while you won't do anything useful for your team. So you basically need to have either 1) High defenses / health + damage or 2) High defenses / health + cc / utility.

In the first category you can put the Tanky Bruisers, who are basically melee fighters that can buy just one offensive item in order to deal good damage and then proceed to build armor, magic resistance or health. The perfect example here is Irelia. She can deal a very high amount of damage while building two, three or four defensive items.

In the second category you can put all the champions that deal little damage but provides your team with heavy cc and utility. The perfect example here is Alistar. He does not deal any serious damage but provides amazing crowd control plus he has a defensive steroid AND an AoE heal. Oh, let's not forget another amazing example: Shen.

Finally, champions like Dr. Mundo or Shyvana do not have enough damage nor crowd control / utility in order to be considered tanks.

This is, in my opinion, what one should know about tanks in League of Legends.