Devataa - A recurring being in mythology referring to a God who is supposed to be immortal. There are gods of all natural elements like Vayu, devtaa of wind, Agni ,devtaa of fire etc.
Asura - A synonym for Demon, also termed as Rakhsasas, who live on earth alongside humans and are constantly fighting the devtaas.
Avatar-Another term for incarnation, when a god lands on earth as a earthly form.
Rishi-Also termed as Sadhu, stands for an ascetic who are supposed to be above worldly pleasures. They possess great powers due to their extreme asceticism. They stay in deep forests and are in constant tapasya or meditation.
Manav- A term for human beings.
Kshatriya-A member of the warrior class of human beings. Most of the rulers and kings are from this class.
Brahmana-A member of the preaching and praying class of humans.
Swarga-A synonym for heaven, one of the three lokas or worlds.
Paatal-Also termed as nether world, it is the underground world and is one of the three lokas.
Bhooloka-The earth which is one of the three lokas.
Boon-A wish usually granted by a God to any person which becomes true.
Shaap- A synonym for a curse, which comes true.
Vedas-The ancient scriptures of Hindu Religion written in four major Volumes. And the source of majority of information on Hinduism.
Yagya - It refers to a form of sacrificial rite performed by Rishis o r kings usually towards some specific purpose. Huge sacrificial pyre is lit and hymns are read. There are usually performed with a specific purpose, like to establish regional superiority for a king, or to ask for a successor to the throne etc.
Avatar - Supposed to be an incarnation of the God on earth in some form.