Always close Bitcoin Core by clicking the "X" or File > Close. Forcing the program to close (via Task Manager) or experiencing a power outage while the database is open is the #1 cause of "Index" corruption.

The wallet.dat or bitcoinwallet.dat file is the core database file for the Bitcoin Core client. It stores critical cryptographic information:

Yes. Advanced users can use the dumpprivkey console command within the Bitcoin Core client to view the raw private keys. However, you should only do this in a secure, air-gapped environment to prevent theft.