Anything, from little facts to long complicated technology explanations.
I truly want to learn some interesting things from different people, I'm ready for surprises.
Maybe you should use the search box first before asking anything if cant find it out in search box then we are here to answer your queries, search for the fundamentals or you can start buy reading the 9 pages white paper of bitcoin.
here is the link:
https://bitcoin.org/bitcoin.pdf