Chain Equipping is the idea of using items that add stats, to satisfy the stat requirements of other items.
For instance, I may need 35 str to use my breast plate enigma. I can easily satisfy that requirement by putting an Annihilus and Hellfire Torch on my character. Now I equip my enigma, and (at level 80) gain around 65 strength. I am now somewhere around 100 strength. I can now equip my Sandstorm Trek, further increasing my strength... and so on and so on. In effect, this allows you to put almost no points in strength and dexterity allowing for more Vitality, and consequentially, more health.
Disadvantage: Any gear swaps may cause your entire character to fall apart.
Example: Swapping enigma for a Skullder's Ire means I lose 65 strength, which means I may now be below the stat requirement of certain items.