Nasdaq is a US stock exchange, and 'the Nasdaq' in market news usually means the Nasdaq Composite index of stocks listed there, which is heavy in technology companies.
The Nasdaq Composite includes several thousand stocks. The Nasdaq-100 is a narrower index of the 100 largest non-financial companies on the exchange.
Why it matters to you
Because it leans toward tech, the Nasdaq often moves more than the S&P 500 in both directions.
FAQ
What is Nasdaq?
Nasdaq is a US stock exchange, and 'the Nasdaq' in market news usually means the Nasdaq Composite index of stocks listed there, which is heavy in technology companies.
What is the difference between the Nasdaq and the Nasdaq-100?
The Composite includes nearly all Nasdaq-listed stocks; the Nasdaq-100 holds the 100 largest non-financial ones.