Darksteel Ingot. Indestructible is a static ability that means that any permanent that has indestructible cannot be destroyed, and cannot be destroyed as a result of lethal damage.
The less-than symbol (<) represents an inequality in which the number or problem on the left is smaller than that on the right; however, it can be reversed (>) to show that the item on the left is greater than that on the right.
Symbol > means greater than; symbol < means less than. For example, 2 < 5, 5 > 2. To remember which is which, observe that both symbols have one pointed side where there is just one end, and one split side with 2 ends.