There are eleven “standard” investing sectors and approximately 375 ETFs that represent them:

Consumer Discretionary (24), Consumer Staples (16), Energy (64), Financials (48), Healthcare (30), Industrials (27), Materials (59), Real Estate (35), Technology (40), Telecom (10) and Utilities (22).

Within each Sector there is a primary ETF which usually has the largest daily trading volume.

The primary Consumer Discretionary ETF is the SPDR (XLY).

The primary Consumer Staples ETF is the SPDR (XLP).

The primary Energy ETF is the SPDR (XLE).

The primary Financial ETF is the SPDR (XLF).

The primary Healthcare ETF is the SPDR (XLV).

The primary Industrial ETF is the SPDR (XLI).

The primary Materials ETF is the SPDR (XLB).

The primary Real Estate ETF is the  iShares (IYR), but the Vanguard REIT ETF (VNO) has a larger market cap.

The primary Technology ETF is the SPDR (XLK).

The primary Telecom ETF is the iShares (IYZ).

The Primary Utilities ETF is the SPDR (XLU).