The Hindus say in life there is ignorance about how things appear and how they actually exist.
We see things as separate from each other. Because we see things as separate, we feel that we are incomplete or we lack something. We feel like we don’t have everything we need/want.
Because you feel u lack something, you desire for something. This causes you to take action, and actions produce Karma. You have to get rid of Karma in order to stop rebirth (which is the goal of Hinduism).
Ex. because I don't look like a celebrity, I now desire plastic surgery. I take action by going to the doctor and getting breast implants.
Though things appear separate, in reality everything is the same thing called Brahman: the ultimate permanent infinite power of the multi-universe that everything runs off of.
Ex. You see a small wave and a big wave in the ocean. You distinguish these waves as separate because one is small and one is big, however, both waves are the same. They both come from the ocean. This illustrates how we see things as separate, but everything is the same—Brahmin.
When you realize that you are Brahmin and everything is Brahmin, you no longer lack anything. You are everything and everything is you. You no longer desire. You have now achieved complete/permanent bliss and happiness. This happiness is not dependent on external things. It's always there no matter what.