In the context of investing, the term market refers to

Even though stocks, securities, and mutual funds are higher-risk investments, many people invest in them because they give higher rate of return.

The rate of return are higher on high risk investments compared with low risk investments. This is because high risk investment have a big possibility of incurring losses, however, if said investment venture is successful and it generates a huge profit, its return is also bigger than when you invest in low risk investments.