Maximum likehood,labeled class and confidence?

Hi all! i hope this is a right place to write my problem with maximum likehood classification. The first time i tried this classification, i got a result with nothing but a black screen in both labeled class band and both confidence band(i used’train on vector’ option). and after i tried a second time with another image(it was a change detection image) for maximum likehood it has both labeled class and confidence band. lastly when i try the ‘train on raster’ option on first image i had labeled class as black screen while had confidence band with some results. Since it was my first time of try it could you explain me what does labeled class and confidence band means? and why did it result as very different each time? how to get rid of getting black screen?

images of spoken topic are shown below

the first try image with geometries that i used on it

the results of first try

the results with change detection labeled class

the results with change detection confidence band

the lastly results of first image with ‘train on raster’ option