Some of the types of ETFs:
Balanced funds - Funds that invest in both stocks and bonds in 
substantial amounts.
Closet index fund - An active fund with higher fees that 
actually tracks an index fairly closely.
Exchange-traded fund (ETF) - An index fund which is traded on 
the stock market.
Index fund - An index fund is a mutual fund that mirrors as 
closely as possible the performance of a stock market index. For example, many 
mutual fund companies have since established S&P 500 index funds to mirror that 
index by purchasing all 500 stocks in the same percentages as the index.
REIT - Real Estate Investment Trust, a type of mutual fund that 
owns portfolios of commercial real estate. There are indexes for this asset 
class, and REIT ETFs follow these indexes.
Grantor Trust - ETF that at creation follows an index but 
remains static and does not attempt to track it. HOLDRs are main adherents to 
this form of ETF.
Unit Investment Trust
Common type of ETF that requires exact duplication of index and prohibits 
derivatives in operation. Like Management Investment Trusts. Examples include 
SPDRs and QQQs.
Naked options trading is very risky - many people lose money trading them. It is recommended contacting your broker or investment professional to find out about trading risk and margin requirements before getting involved into trading uncovered options.