json rpc – What data i can save?

i’m make one application about bitcoin, and I’m searching that data i can save, I’m read that the public key i can save in my database and privit key no, but i dont know, what more data i can save, I explain?, I’m would like to guide me, I have also read about getblock, but I don’t know what it really is.

To be more specific, I would like to know exactly what data I have to save in the database and what performs each of the aforementioned functions of bitcoin.