Proshares Ultra S&P500 Experiences Big Inflow
July 06, 2012 at 11:26 AM EDT
Symbols mentioned in this story: SSO, ANF, ACN, ACCO Exchange traded funds (ETFs) trade just like stocks, but instead of ''shares'' investors are actually buying and selling ''units''. These ''units'' can be traded back and forth just like stocks, but can also be created or destroyed to accommodate investor demand.