# What do the outputs of the function dlmSmooth from R's dlm package mean?

In the vignette for the R package dlm: link on page 12, the author runs the function dlmSmooth to smooth the data and the function returns an object which is assigned to gasSmooth. Now, gasSmooth$s is described in the package help as: Time series (or matrix) of smoothed values of the state vectors. The series starts one time unit before the first observation. They say: Based on the fitted model, we can compute the smoothing estimates of the states. This can be used to obtain a decomposition of the data into a smooth trend plus a stochastic seasonal component, subject to measurement error. and then run: gasSmooth <- dlmSmooth(lGas, mod = dlmGas) x <- cbind(lGas, dropFirst(gasSmooth$s[,c(1,3)]))
colnames(x) <- c("Gas", "Trend", "Seasonal")


The author in the vignette selects to plot columns 1 and 3 of this timeseries matrix, but how do they know that these states represent the smoothed trend and the seasonal trend?