I don't use Avast; but many anti-virus programs run continually in the background, but they also let you conduct a scan upon request. They have options to make that scan much more thorough than what is done when it is normally running. You, or whoever set up your computer, probably specified a light scan be done at regular intervals; perhaps daily or weekly. But any time you suspect that there might be malware on your computer, it is good to have it conduct a scan of your entire computer. Such a scan will be time consuming and will slow down your computer while it occurs, but it might just catch something that it otherwise wouldn't have.
- Lynn
