What are smoothed variables

Hello,
I am new to this topic. I have been going through some questions? I don’t get what smoothed variables are and how to generate initial values. None of the papers and textbooks explain this.

Smoothed variables are the best estimates of unobserved variables, given all the sample information used for estimation. The are the objects coming out of the Kalman smoother. See e.g. Hamilton’s textbook.