Forecasting analysis

I have a database with historical data and would like to understand how I relate the historical average to the evolution of historical data. Is it possible to make a relationship between these two things?

Thank you very much!
What do you mean by " historical data"? A few examples would be good.

(A time series of economic growth data from 1950 to today is historical data. The other person here writing about manuscripts from the Roman time is historical data. The name of the kings in Sweden is historical data.)

What do you mean by " the evolution of historical data"? Does data "evolve"?

"the historical average" of what? There are many ways to compute an average.