How and where is data stored in ethereum blockchain? Is it on chain or off chain or where? Is it hashed or stored in raw format? How are we able to see data through ethrscan if it is hashed before storing?
A blockchain is a network of nodes which are accessed by decentralized apps / Dapp-s.
The details on how Dapp-s access blockchains are in this article -
What a Dapp really is