Does anti virus really put out the viruses?

Hello,
hi there, i woul just like to ask abou that viruses thing. One time a Trojan named virus appeared in my compuiter while i'm browsing a site. And i opened my anti virus scanner. It started to scan the files on my computer bt no files was infected? I dont know. And I changed the site of that virus int he adrees bar. And run other site. And it's gone. it disappears. But i don't know if it really fades in my computer? I just wanna ask. Thanks