What is Stochastic-local volatility model?

A stochastic-local volatility model (SLV) lets the underlying’s volatility be the product of a function of time and spot and a stochastic factor:

with a mixing weight $\lambda\in[0,1]$ scaling the volatility of variance: $\lambda=0$ reduces the model to local volatility and $\lambda=1$ with $L(t,S)=1$ to Heston.