iMac voiceover reads out loud instead of displaying them on screen

When I type in letters in for instance Google, and type at the same speed I normally do, the letters won't appear. If I press the letter longer the iMac says which letter it is and than shows it. Someone said it was the Voiceover option that is activated but that is not true. What should I do to shut this option of?

[Re-Titled by Moderator]