USA market indices (most popular) and what they mean

1) S&P 500

• measures the stock performance of 500 large companies publicly listed on stock exchanges in the United States
• considered one of the best representations of the U.S. stock market
• though all companies in it are listed in the USA, it includes many multi-national companies
• companies in the index derive on average only about 70% of their revenue in the USA
• capitalization-weighted: the 10 largest companies in the index account for 1/5 of its performance
• not necessarily the 500 biggest companies listed in the USA; there are many rules governing how the components are selected, including that they cannot be ADRs and ETFs
• associated with many ticker symbols, including: ^GSPC, INX, and $SPX, depending on the source
• popular tracking ETF: SPY
• inverse ETF: SH
• interesting note: Tesla (TSLA) is not part of the S&P 500 even though many would assume it is

2) Dow Jones Industrial Average (DJIA), a.k.a. Dow 30, a.k.a. The Dow

• measures the stock performance of 30 large companies listed on stock exchanges in the United States
• represents over $8.3 trillion in market cap value as of the end of 2019
• the “industrial” name is largely historical, and many of the modern 30 components have little or nothing to do with traditional heavy industry
• not the best representation of the USA market because it’s not weighted by market capitalization and does not use a weighted arithmetic mean (in other words, it’s a price-weighted index, i.e. simply the sum of its constituent stocks’ prices, adjusted for stock splits and dividends)
• second-oldest U.S. market index after the Dow Jones Transportation Average
• associated ticker symbols: DJIA, ^DJI
• popular tracking ETF: DIA
• inverse ETF: DOG

3) NASDAQ Composite

• tracks the equities listed on the NASDAQ stock exchange
• happens to be heavily weighted towards IT
• though it is one of the 3 most-followed indices in the USA stock markets, the NASDAQ-100, which accounts for over 90% of the NASDAQ Composite's movement, is more popular for tracking by ETFs, the most popular ETF being QQQ
• associated ticker symbols: ^IXIC, COMP

4) NASDAQ-100

• measures the stock performance of 100 of the largest non-financial companies listed on NASDAQ
• financial companies are excluded, they have their own index
• accounts for over 90% of the NASDAQ Composite's movement
• associated ticker symbols: ^NDX, NQX (reduced 5x)
• popular tracking ETFs: QQQ, TQQQ (3x-leveraged)
• inverse ETFs: PSQ, SQQQ (3x-leveraged)

5) Dow Jones Transportation Average

• gauge of the American transportation sector
• oldest U.S. market index

6) CBOE Volatility Index

• ticker symbol: ^VIX
• a.k.a. The Fear Index
• formulates a theoretical expectation of stock market volatility in the near future
• quotes the expected annualized change in the S&P 500 index over the following 30 days, as computed from options-based theory and current options-market data
• the higher — the “scarier”, but not necessarily bad; a higher VIX predicts that the market will move sharply, whether downward or upward
• corresponding ETFs usually reset daily and are not recommended for long-term holds

7) Russell 2000 Index

• USA small-cap index
• associated ticker symbol: ^RUT
• popular tracking ETFs: IWM, VTWO
• inverse ETF: RWM

8) others

Dow Jones Utility Average, S&P 400, S&P 600, S&P 1500, Russell 1000, Russell 3000