Quant investing is a broad catch-all term for using math, rules, and logic to invest. At its core, it implies no human decision-making. This means there is no gut, intuition, emotion, or biases in buying or selling.
As a stock market becomes more mature, the amount of rules vs humans in investing goes up dramatically. In India, the last two years have caused our markets to mature quicker than the entire decade before that. This means, passives are now mainstream. Usually, while passives track an index, active funds try and beat the index by taking stock/asset level calls.