Armored like an Abrams.
The warrior is the premiere tank class in Everquest, with access to heavy armor and the best single target threat in the game. They also have higher hitpoint values than any other class, and special access to a variety of class-restricted weapons that give them particularly good threat generating abilities.
Skilled warriors will switch between two handed and one handed weapons with a shield in order to maximize their threat generation. They receive most of their combat skills at lower levels; more than just about any other class, helping them to be a cut above the hybrids at tanking at just about every level. While they are constantly in demand for groups, warriors are very poor soloers, with limited ability to do damage and survive on their own without healing support.
The primary function of the warrior is to take the monsters that are on the group and to get them to focus on him until they are dead. They have some abilities to build threat on multiple monsters, but they are really best at sticking to single targets. Warriors work best with proper crowd control support to ensure that they don't have more enemies than they can handle at one time.
Warriors wear plate armor, and can use all sorts of weapons. Large races generally make better races for warriors than others, particularly because of their slam ability but also because of their higher strength and stamina. Stamina is absolutely the most important ability for a warrior, as their prime focus throughout their career is to tank. For those purposes, the Ogre or Troll is the absolute best choice for a warrior, followed closely by the Barbarian.
In terms of what they do regularly, warriors are not a significantly challenging class to play so long as they understand their role and stick to it while fighting enemies. In raid settings, they tend to have a very high level of responsibility, as they will either serve as the main tank or a crucial offtank there to pick up any extra monsters that would otherwise rampage through the weaker classes. The disciplines that they gain access to after level 50 add a fair amount of complexity to the class, but don't really come into play until much later.
Warriors should focus on their strength, agility and stamina, but as mentioned before, stamina remains the highest priority to build. Choose the warrior if you want to tank - if you don't, pick another class.