With all due respect, it's never too late to learn. Very often in target archery especially with compound bows they're quite common. Here is a quick summary... I have a clarifier in one of my target bows, but have never considered using one in my hunting bow. Nonetheless, some may need/want them simply due to vision correction issues.
Originally Posted by mossyhorn
Q: How do I know if I need a Verifier or a Clarifier?
A: A Verifier is used when you shoot with pins to clear up the pins, and a Clarifier is used when you shoot with a scope and a lens to clear up the target.
Q: What is a Verifier?
A: A Verifier is a lens installed in the peep that will allow you to see the pins clearly. It will not clear up your target. The verifier works similar to reading glasses and is made for older shooters who have difficulty seeing objects at close distances.
The reference to a "scope" is a glass insert in the sight window, usually 1-2x magnification. Again, often seen/used in target archery.