Some people find anal sex pleasurable. Although people have different beliefs, sexual contact (which may include oral, vaginal, or anal sex) is neither wrong nor bad as long as both people feel ready, and are making sure they get consent from their partner. Though pregnancy cannot happen with anal sex, sexually transmitted infections can easily spread. So condoms are necessary for anal sex.
Also a lot of additional lubrication is important, because the anus does not produce lubrication. It’s important to go slowly, because the tissue in the anus is delicate and could be damaged or torn. If people are switching from vaginal to anal sex, it’s important to add more lubricant before entering the anus. Going back to the vagina after being in the anus without being throughly washed is not a good idea because it can bring infection into the vagina.