Explain this paragraph to a child:

A local volatility model, in mathematical finance and financial engineering, is an option pricing model that treats volatility as a function of both the current asset level S t S_{t} and of time t t. As such, it is a generalisation of the Black–Scholes model, where the volatility is a constant (i.e. a trivial function of S t S_{t} and t t).  Use some words in all caps in your response, but those all-caps words should appear at most 14 times.
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