Sometimes you may get files from mail these files may be infected by any virus or Trojan, or any malware. If you want to scan your files online, VirusTotal is online services that help you to scan your individual files online. it is very simple and no download is required for using VirusTotal.
When you scan a file online VirusTotal will scan more than 40 antivirus engines it includes Kaspersky, McAfee, NOD32, AVG etc. After scan your files the result will appear each antivirus engines result one by one.