A rebound can apply to everything from a company, to an individual stock price, to the market. A rebound is defined as a positive turnaround after a period of negative behavior.
For a company, this could mean recording a profit after a period of loss. For stock, a rebound is when the price rises after a previous drop. For the market at large, this could be economic recovery after a recession.
A recent example of a market rebound was during the COVID-19 outbreak. Early in 2020, the economy began to see a downturn as uncertainty in the market took over. But soon after, the market saw a rebound as presumably investors suspected a return to normality and began to reinvest.