I read in some forum that players can only equip one exotic item at a time. Is this true? And what happens if you try to equip two?
You can equip two exotic items: one weapon and one armor.
Whenever you have an exotic weapon equipped, other exotic weapons in your inventory will appear disabled (dark yellow) and you're unable to equip them until you unequip the one you have equipped.
The same holds for exotic armor items, other exotic armor items will appear with the same dark yellow cast and you will be unable to equip them.