The markets are recovering, albeit slowly, and investors are wading back in to buy exchange traded funds (ETFs). Most of those investors, at one point or another, will come across these five ETFs, the most heavily traded ones in the markets.

SPDRs S&P 500 (NYSEArca: SPY), currently up 15.6% year-to-date, with average daily trading volume of 189 million, corresponds to the price and yield performance of the S&P 500 Index. The fund has a net expense ratio of 0.09%.

Sector allocations: information technology, 18.6%, financials, 15.2%, health care, 13.1%, energy, 11.7%, consumer staples, 11.6%, industrials, 10.2%, consumer discretionary, 9.2%, utilities, 3.7%, materials, 3.5%, telecom services, 3.2%

PowerShares QQQ (NasdaqGM: QQQQ), currently up 38.4% year-to-date, with daily average trading volume of 133 million, seeks to track the Nasdaq-100 Index. The fund consists of all stocks in the Index, which includes 100 of the largest domestic and international nonfinancial companies. QQQQ has an expense ratio of 0.2%.

Sector allocations: consumer discretionary 13.3%, consumer staples 1.1%, health care 16.3%, industrials 4.9%, info. tech. 63.1%, materials 0.6%, telecom services 0.8%

Financial Select Sector SPDR (NYSEArca: XLF), currently up 16.1% year-to-date, with average daily trading volume of 112 mil, tries to reflect the returns and characteristics of the Financial Select Sector Index.  The fund has an expense ratio of 0.21%. Top holdings include JP Morgan (NYSE: JPM) and Bank of America (NYSE: BAC).

iShares Russell 2000 Index (NYSEArca: IWM), currently up 19.8% year-to-date, with average daily trading volume of 72 million, tries to mimic results that correspond to the price and yield performance, before fees and expenses, of small capitalization sector of the U.S. equity market, Russell 2000 Index, which represents around 2,000 smallest companies in the Russell 3000 Index. The fund has an expense ratio of 0.24%.

Sector allocations: financial services, 20.5%, consumer discretionary, 16.8%, technology, 15.8%, health care, 15%, materials & processing, 8.2%, producer durables, 8.1%, utilities, 5%, other energy, 3.9%, autos & transportation, 3.5%, consumer staples, 2.6%

UltraShort QQQ ProShares (NYSEArca: QID), currently down 9.2% in the last month, with daily average trading volume of 36 million, seeks daily investment results that tracks twice the inverse of the daily performance of the NASDAQ-100 Index. Note the ETF tries to reflect a -200% return of the Index for a single day. The fund has an expense ratio of 0.95%.

Max Chen contributed to this article.

Tags: Asset Class ETFs, Financial, IWM, Large-Cap, Long-Short ETFs, NASDAQ, QID, QQQQ, Russell 2000, S&P 500, Sector ETFs, Small-Cap, SPY, XLF