"Quants" are traders who use quantitative analysis to make financial trades. Computer-based quantitative analysis, which studies how amounts, or quantities, relate to each other, is the most common mathematical model used by trading houses.
Do you need maths for stock market?
Math is a tool you can use to improve trading, but it is not required for trading. Most traders use at least some simple math, such as selecting stocks in part by price/earnings ratio, or managing risk by volatility targeting and stop losses.