Well here's the scoop, I'm surprised no one more qualified to answer these questions is doing so (i.e. a women), but I'll try my best.
A veil is a mantilla. Its a head covering that Catholic women traditionally wear. Here is a web page showing the 2 most common types of veils. The one on the left is more modern 1950s/1960s style while the one on the right is more traditional. You'll usually see a mix of the two styles at traditional chapels.
http://www.ocdsrose.com/chapel_caps.htm
Women can also just wear a hat instead of the veil, but many just prefer the veil I guess.
Why isn't Amen said? Its because the Priest when he distributes communion says the Amen for you. "Corpus Domini nostri Jesu Christi custodiat animam tuam in vitam aeternam. Amen" "May the Body of our Lord Jesus Christ preserve thy soul unto life everlasting. Amen." So there is no need for you to say Amen. All of the Eastern Rite masses I've ever attendend (Ukranian, Armenian, Melkite, Syro-Malankar) similarly don't require you to say Amen either. Its only Novus Ordo where people say Amen for commmunion.
Everyone kneels for communion and receives on the tongue. Every once in a while you'll see somebody standing for commmunion and thats because they have bad knees. So unless you have a medical problem which prevents you from kneeling you have to kneel at the altar rail to receive communion.
Ah ha! Thank you! Great explanation!
Thank you for the veil explanation. But my original question still stands, why must a woman's head be covered?