Often, a special sector index is created for the fund.
Fund by buying shares that are part of the index has the ability to imitate the index results.
Funds can also invest in futures, such funds are burdened at the expense of rolling contracts and this is called contango.
Information on the issuer of the ETF fund
Before you invest in an ETF, you should first become familiar with how it works.
Also on the issuer side of the fund will find information such as: what is the total commission of the fund, what specific assets invest the fund, what are its goals, what are its results so far.