Confusion regarding Cell column in the sample.txt file and the data in forest_t3.tif

[soumyadiptapete]

I was trying to follow the steps in https://ecology.ghislainv.fr/forestatrisk/notebooks/get_started.html#1.-Data. I am confused about the Cell column in the sample.txt file generated.

Also, what is the forest_t3.tif file used while prediction? Is it the list of pixels for which predictions needs to be done?