The Buddhist "rules" are guidelines to help us live in harmony with others and create happiness for ourselves. At the very least, we try not to harm others. And as much as we can, we try to help.
My teacher, Ven. Thubten Chodron, speaks of our mouths being our own personal weapons of mass destruction. In a careless moment we can destroy a lifetime of friendship. On a larger scale, a few lies can bring fear to thousands and even spark global conflict.
A person unfamiliar with Buddhism could easily inspect a Buddhist temple filled with statues and wonder, "Are these people worshiping idols?" Your question may help others feel more comfortable with Buddhists and Buddhist settings, so thanks for asking.
His Holiness the Dalai Lama says that you can use any of the Buddha’s teachings that help you in your life without becoming “Buddhist” or adopting the Buddhist worldview.
The short answer: nirvana is the state of having eliminated all our disturbing emotions and distorted attitudes so that they can never arise in us again. The long answer...