This is normally an indication that you or rather the scan detected something and a pop-up alert should have appeared, requiring your input.
This is dependant on your avast version and settings.
At the end of the scan you should have a list displayed or you can right click the skin and select, Last scan results (only available for that scan session in the home version) or View scan report. These options are avast version dependant.
What version of avast do you have Home or Pro ?
