Quantitative finance is the discipline of using mathematical models in order to help make investment decisions. On-topic questions will only approach this topic from a programming point of view, and include a language tag such as r, matlab, python, etc. Theoretical or purely mathematical questions are not on-topic at Stack Overflow.
Quantitative Finance is a set of methods of approaching finance in a principally technical, quantitatively supported manner.
This represents a wide-reaching suite of mathematical approaches to many subject of interest in a domain of finance, that not always had such comfort of purely quantitative methods of work.
Application domains of the state-of-art quantitative finance methods start from time series data analysis, cover technical analysis ( TA ), modeling both market risk & approaches to risk management techniques, create support for a detailed financial products' engineering, introduce advanced applied statistics into predictive analyses, into risk adjusted portfolio management decisions and as such also include all recent promoted flavours of quantitative tools like machine learning, in it's narrow sense of supervised learning methods, various stochastic methods for options pricing models, Hidden Markov models ( beneficial by introducing an innovative view on a set of indirect, hidden, factors involved in a model of an externally observable process ), Artificial Intelligence tools ( somewhat over-hyped ) in it's very narrow sense, with a common use of artificial neural networks ( ANNs ), recurrent NNs, more recently deep-learning NN, with a few attempts to inject even LSTM NNs and some more sophisticated types of automated ( unknown ) model creation strategies.
If your question concerns theoretical topics on quantitative finance or practical topics which are not about implementation you might want to ask the question on quant.stackexchange. In particular, this tag should never be used a alone but always in combination with a specific programming language (like for example r, python, sas, matlab).
