For the vast majority of Americans, investments fall into broadly three categories: stocks, bonds and real estate, with the latter usually being the family home. Perhaps some people will own some commodities.
Basically, that's it. But it doesn't have to be.
For those willing to put in some effort to educated, the fine art market provides opportunities to add some return, while reducing overall risk in a portfolio. Still, it isn't without potential problems. Read more here.