time series – What effect does the addition of [“Options”] have in the following use of TimeSeries?

In an example found at Use Time Series Processing for Financial Analysis the time series

prices = sp500["PathComponent", "Adj Close"]   

is followed by

simpleReturns = TimeSeries[Ratios[prices] - 1, prices["Options"]]

to create a time series of x1/x2-1 price returns. That is the normal way to calculate price returns. But, what is the prices[“Options”] part supposed to do? TimeSeries[Ratios[prices] - 1] returns exactly the same thing. I don’t understand the prices["Options"] construction.