Zero (0), one (1), and infinity (∞) are the indiscrete numbers. They represent absolute, indivisible values. What makes them special?
They exhibit qualities whereby operations with other (discrete) numbers make no difference:
0 is the infinitesimal extreme. Multiply it by anything discrete, and it is still nothing. Sum zero with anything discrete, and the sum is equivalent to it.
1 is the singularity, the extremity of discretion. Multiply anything discrete by one, and it is still itself.
∞ is the infinite extreme. Multiply infinity by anything discrete, and infinity is still infinite.
What makes these numbers so unique is that they go beyond the scope of the mathematical rule of discretion; they transcend discretion and expose holes in mathematics through reasoning at the extremes, including the realization that they are philosophically equivalent! Furthermore, they are perfect symbols for each other equivalency about whatever subject; what's most useful is realizing how each of the indiscrete numbers is equivalent to each other in the context of the subject. This is what makes them the fundamental, symbolic equivalencies – metaequivalencies, by that perspective.
In describing all that there is, the universe, the fundamental equivalencies represent the most philosophically precise perspectives about the value of the universe:
0 - the universe has no value; how\why would you value all that there altogether?
1 - the universe is simply a whole, the ultimate whole infact. Any discretion is only convenient selection done by the human mind.
∞ - the universe goes on forever, it has infinite value.
What's great is the indiscrete numbers apply not only to the absolute concept of the universe, but to individual aspects we can select to discuss as well. We can find equivalencies at any scope. What is an equivalency, exactly? Wherever extremity is considered, you find that the barriers between definitions break down, and become purely dependent on perspective. You find that, since extremity is possible in any scenario, scenarios are not truly limited except by our artificial restrictions that we have decided to imagine. In reality, everything and each philosophically sound explanation is equivalent, continuous, in unity. By finding the equivalencies in the context of the most confusing philosophical questions, explanations can be found for the way of things; insights can be realized through metacognitive reasoning.
Besides explanation of their usage, perhaps the best way to familiarize yourself with the idea of equivalencies is by example.