There is a dangerous trend among young men these days, likely the fault of the pornography industry which I cover in another article linked above. For whatever reason, anal sex has become the newest thing that men of this generation expect women to be receptive to. I preface this by saying that consenting adults have the right to do whatever they like but before they do it helps to be knowledgeable.
First of all, actual pleasure is a major factor. While I am sure the men out there just love it, it is rare and for the most part almost impossible for a woman to feel anything but pain and discomfort from having anything in her anus, let alone a penis. The anus was not designed for uptake and it usually hurts. the only way a woman can take pleasure from anal, and it doesn't happen often, is if the penis somehow presses on the vaginal wall from inside the anus. this is possible but rare. Many women may be paid by men's magazines and the pornography industry to claim they enjoy anal, but I assure you they do not. Take some consideration for what your partner is feeling, that's just basic relationship courtesy. You are too immature for any sexual contact until you understand and practice this fact. You should be unwilling to do to anyone what you would be unwilling to have done to you.
On top of general concerns of discomfort, there is an added concern of infection. the anal tissue tears very easily, much more easily then vaginal tissue. Both parties should be aware of the potential for infection before engaging in anal. Using a condom should reduce this risk of course, as well as using lubricant generously, which may also make it less painful.
Ultimately there is nothing wrong with anal if both parties are truly willing and aware of the risks and consequences. It has not been my intention here to condemn the act itself or any act at all.