1. the state of absolute peace, happiness, and joy = nirvana
Nirvana is a term related to Buddhism that has to do with feelings of absolute peace, happiness, and joy. It is something that every Buddhist is trying to achieve through meditation and good deeds and leading a good life, although not many succeed.
2. those who delay entering heaven to help other people = bodhisattva
Bodhisattva is a term related to Buddhism which refers to people who can easily reach nirvana and go to the light, but choose not to until they've tried to help others in need. They feel compassionate and empathetic towards others and will not go anywhere until they've helped others.
3. the technique through which you can calm your mind = meditation
Meditation is a very important technique when it comes to Buddhism. Buddhist meditate quite often when they want to relieve stress, rid themselves of bad thoughts and feelings, and just relax after a long and tiresome day.
