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.
On a number line the greater than symbol . is greater than or is to the right of on the number line. Then ...they show the  symbol which is less than or is to the left of on the number line. They show a number of examples using these symbols. They proceed to the greater than or equal to symbol and the less than or equal to symbol. Once again they do many examples and explain as they do them.